In the 23rd century, a mysterious probe suddenly appears on a direct course for Earth and begins disabling everything in it's path. Meanwhile on the planet Vulcan, Admiral James T. Kirk and the crew decide to go home and face punishment for their unauthorized mission to the Genesis planet to rescue Captain Spock. As they begin their return to Earth in the Klingon Bird of Prey, the probe already arrives there and it's signal causes the planet's power systems to lose power and block out the sun. The probe's signal is directed at the oceans. The Federation sends a warning about the probe and after Admiral Kirk receives it, Spock uses the ship's computer to determine if his theory, that the probe is signaling a creature in Earth's ocean, is correct. Spock's research proves that it is directed at humpback whales, which have been extinct for centuries. To save Earth, the crew must travel back in time to find humpback whales to reply to the signal. After a sling shot around the sun, the crew find themselves in 1986. Now they must find a pair of humpback whales and keep from being detected with only have 24 hours to save humanity.

William Shatner - Admiral Kirk

Leonard Nimoy - Captain Spock

DeForest Kelley - Dr. Leonard McCoy

James Doohan - Capt. Scott

George Takei - Cmdr. Sulu

Walter Koenig - Cmdr. Chekov

Nichelle Nichols - Cmdr. Uhura

Jane Wyatt - Amanda

Catherine Hicks - Dr. Gillian Taylor

Mark Lenard - Ambassador Sarek

Robin Curtis - Lt. Saavik

Robert Ellenstein - Federation president

John Schuck - Klingon ambassador

Brock Peters - Adm. Cartwright

Michael Snyder - Starfleet comm officer

Michael Berryman - Starfleet display officer

Mike Brislane - Saratoga science officer

Grace Lee Whitney - Cmdr. Rand

Jane Wiedlin - Alien comm officer

Vijay Amritraj - Starship captain

Majel Barrett - Dr. Christine Chapel

Nick Ramus - Saratoga helmsman

Thaddeus Golas - Controller 1

Martin Pistone - Controller 2

Scott DeVenney - Bob Briggs

Viola Stimpson - Lady in tour

Phil Rubenstein - Garbageman 1

John Miranda - Garbageman 2

Joe Knowland - Antique-store owner

Bob Sarlatte - Waiter

Everett Lee - Cafe owner

Richard Harder - Joe

Alex Henteloff - Nichols

Tony Edwards - Pilot

Eve Smith - Elderly patient

Tom Mustin - Intern 1

Greg Karas - Intern 2

Raymond Singer - Young doctor

David Ellenstein - Doctor 1

Judy Levitt - Doctor 2

Teresa E. Victor - Usher

James Menges - Jogger

Kirk R. Thatcher - Punk on bus

Jeff Lester - FBI agent

Joe Lando - Shore Patrolman

Newell Tarrant - Cmdr. Rogerson

Mike Timoney - Electronics technician

Jeffrey Martin - Electronics technician

Sgt. Joseph Naradzay - Marine sergeant

1st Lt. Donald W. Zautcke - Marine lieutenant

Joseph Adamson - Doctor

Monique DeSart - Madeleine

Stephen Liska - Torg

Madge Sinclair - Saratoga captain

The device Dr. McCoy uses to heal Chekov's head injury is part of a model of Spock's Vulcan Transport from the first movie.

The punk on the bus is Kirk Thatcher who also wrote and performed the song that is playing on his stereo at the time.

Some shots of the whales were in fact four foot long animatronics models. Four models were created, and were so realistic that after release of the film, US fishing authorities publicly criticized the film makers for getting too close to whales in the wild. The scenes involving these whales were shot in a high school swimming pool. The shot of the whales swimming past the Golden Gate Bridge were filmed on location, and nearly ended in disaster when a cable got snagged on a nuclear submarine and the whales were towed out to sea.

The film was originally supposed to have Eddie Murphy instead of Catherine Hicks. Murphy was supposed to be a professor concerned with UFO's who spots the de-cloaking Klingon ship at the Super Bowl. Apparently, all others are convinced the ship is a half-time special effect while Murphy believes it is real. Paramount declined this script for two reasons: Paramount didn't want to combine their two most profitable franchises (Star Trek and Beverly Hills Cop), and Murphy had signed on to do The Golden Child instead.

According to actor George Takei, when McCoy, Scotty and Sulu are standing in front of the building with Yellow Pages ad, a door opens and an Asian woman appears. The scene in the movie ends at this point but originally this woman was to begin shouting for a young boy named Hikaru, who would run into Sulu. Sulu would realize that this boy was his great-great-(etc.) grandfather. The young boy hired for this scene began to cry on the set before the shot and they were unable to get him to do the scene. With no one to replace him, the scene was never shot.

Sulu was supposed to leap into the Huey helicopter when the pilot was outside, looking the other way, and make off with it. George Takei had just run the San Francisco marathon when they were supposed to shoot this scene, and was too sore to leap into the 'copter. They tried having a grip throw him in, but couldn't get it to look realistic, so the scene was cut. In the final edit, Sulu is shown talking to the pilot, then shows up flying the helicopter a few minutes later.

Cameo: Bob Sarlatte as the waiter in the restaurant.

The Cetacean Institute is actually the Monterey Bay Aquarium in Monterey, California. The Institute's logo also belongs to the Aquarium.

When Kirk, McCoy, and Gillian first enter the hospital and are walking around trying to locate Chekov, a voice on a loudspeaker in the background says "Paging Dr. Zober... Dr. Sandy Zober." Sandra Zober was director/star Leonard Nimoy's wife at the time.

One of the officers on the Saratoga (the one who announces that the thruster controls are offline) is of the same alien race as the Federation President in Star Trek VI - The Undiscovered Country. This race has never been officially named, but some promotional materials identify the race as the Efrosians (named after Mel Efros, unit production manager for Star Trek IV).

During Spock's memory tests, the computer speaks very rapidly, almost too rapidly to discern. The first question it asks Spock is, "Who said 'Logic is the cement of our civilization, with which we ascend from chaos, using reason as our guide'?"

The time-travel method used in the film comes from the original series episode "Tomorrow is Yesterday."

A scene written for but cut from the film explained why Saavik stays on Vulcan: she is pregnant with Spock's child, stemming from an event in Star Trek III: The Search for Spock. This was the character's final appearance in a Star Trek film.

The success of this film spurred American TV networks to explore the possibility of a new Trek TV series. This led to the creation of Star Trek: The Next Generation the following year.

The miniature of the Spacedock interior (some fifteen feet across) had been destroyed at the end of production on the previous film and had to be rebuilt from scratch.

The captain of the USS Saratoga, seen at the start of the film, was the first female captain ever seen in a Star Trek story. The success of this film led to offers by several US TV networks to produce a new Trek TV series. Instead, Paramount gave the green light to produce the syndicated Star Trek the Next Generation.

Scenes of the Enterprise's final moments and its self-destruct were reused from "Star Trek III - The Search for Spock".

One early draft script was subtitled "The Trial of James T Kirk". This script involved Kirk being court-martialed at the request of the Klingons, who were indignant about the events in Star Trek III: The Search for Spock (1984). One particularly interesting facet of this script is that it included the character of Harry Mudd as a character witness. When the time-travel script was approved instead, the trial was included as a minor sequence. The trial-by-Klingons idea (and portions of the dialogue) was later re-used in Star Trek VI: The Undiscovered Country.

As part of a deal with reincarnating Spock in the previous film, Leonard Nimoy took the director's seat.

When Chekov is running through the Enterprise (the aircraft carrier), trying to get away from the Marines, the words "Escape Route" and an arrow can be seen on the bulkhead walls.

Towards the end of the film, the characters evacuate the Klingon ship, and end up jumping in the water and splashing around. This was not scripted - Jimmy Doohan slipped, the rest of the actors followed and the 2nd unit director kept rolling.

The 'USS Enterprise CVN-65' was actually The USS Ranger CV-61. The Enterprise was out to sea during filming.

The computer graphic consoles that became standard on the 24th century Star Trek bridges and also called "Okudagrams" (named for designer Mike Okuda), make their first appearance on the bridge of the U.S.S. Enterprise, NCC-1701-A. It is also the final appearance of the entire original Star Trek movie bridge set as only small parts were reused for Star Trek V - The Final Frontier.

According to Spock's computer on Vulcan, Kiri-Kin-Tha's First Law of Metaphysics states that "Nothing unreal exists".

Kirk Thatcher did such extensive work on the film that he was promoted from "Production Assistant/Visual Effects" to "Associate Producer" by the end of the film.

Scenes filmed on location in San Francisco marked the first time any Star Trek installment had been filmed outside the Los Angeles region.

When Nicholas Meyer was asked to help with the script, the first thing he wanted to do was change the location from San Francisco to Paris because he had previously written and directed a movie about time travel involving San Francisco (Time After Time). But since Star Fleet is supposed to be located in San Francisco, he was overruled.

The scene with Chekov and Uhura kneeling on rocks looking at the Aircraft Carriers was shot in San Diego at North Island Naval Air Station.

It is often claimed that this is the only Star Trek film where no weapons are fired. This is incorrect, as Kirk uses his phaser to weld a door shut, and the whaler fires its harpoon. Chekov also tries to use his phaser, though it doesn't work. It is also one which no cast member from this film is killed, as the only deaths were from the film clip from Star Trek 3.

The whale hunters speak Finnish.

The film bore the dedication, "The cast and crew of Star Trek wish to dedicate this film to the men and women of the spaceship Challenger whose courageous spirit shall live to the 23rd century and beyond..."

The computer that Scotty uses to show transparent aluminum was originally going to be an Amiga, but Commodore would only provide a computer if they bought it. Apple was willing to loan them the Mac.

When the alien ship is approaching Earth at the beginning to look for the humpback whales, there were originally subtitles saying things like "Where are you? Can you hear us?". The studio wanted to keep them despite Leonard Nimoy's objections. In the first test screening, however, test audiences indicated the subtitles were unnecessary so they were cut.

For the shot of Sulu flying the helicopter over San Francisco bay, the filmmakers tried to get a pilot to fly a Huey, but they were unable to. The long shot was accomplished using a radio controlled model from Japan.

The Probe is modelled after Rama from Arthur C. Clarke's "Rendezvous with Rama".

The scene with Chekov and Uhura asking passerby where Alemeda and the U.S. Enterprise were was completely unscripted, as was the young lady's clueless response, "Ooh, I don't think I know the answer to that one - I think it's in the bay, in Alemeda." Crew had to chase her down after the shot was taken to get her to sign a SAG waiver and permission to use her in the film.

The scene with the punk music on the bus was written by Nicholas Meyer to revive a scene that was cut from his movie "Time After Time", that had H.G. Wells encountering a teenager with music blaring from a boom box.

While attempting to escape from the security agents aboard the USS Enterprise, Chekov tosses his phaser to one of the agents; although it is representative of twenty-third century technology, it is never retrieved.

Revealing mistake: When the cloaked ship lands on the grass, a trash can is crushed. As the earth (grass) moves down under the pressure of the heavy ship, the grass blades remain pointing up.

Continuity error: The candle and beer in the restaurant.

Boom mike visible: After the President gives his warning, Kirk gets up to talk to Spock.

Continuity error: At the Cetacean Institute after Spock's mind meld with the whale inside the pool, Gillian and Kirk find him dressing up again but he looks completely dry. Although we may assume that 23rd century clothes will dry up in a split second, Spock should still be wet.

Error in geography: The shot of the whales swimming away at the end of the movie was set in San Francisco, but the footage was filmed off the coast of Hawaii (The Big Island is visible in the background).

Continuity error: The hand that Kirk uses the phaser with when rescuing Chekov.

Error in geography: After leaving the Cetacean Institute, Kirk and Spock discuss the whale situation; from the view of the Golden Gate Bridge they have returned over the bridge from Sausalito to San Francisco. The scene changes and when we return to Kirk and Spock, they are back in Sausalito, being offered a ride by Gillian "back to" San Francisco.

Crew or equipment visible: Sound stage wall visible through the hatch that Kirk blows after the Klingon ship crashes into San Francisco Bay.

Continuity error: The Klingon ship is shown hovering above the whaler with the whaler deep in its shadow. When they cut back the bridge of the whaler, they're back in the sunshine. They cut back to show the Klingon ship hovering over the whaler, and it is once again in shadow.

Error in geography: Kirk and Spock ride a San Francisco "Muni" bus to the "Cetacean Institute" in Sausalito. However, Muni does not run any buses over the Golden Gate Bridge to Marin County, where Sausalito is located.

Revealing mistake: During landing of the ship, garbage cans are "blown over" into the prevailing wind, and can be seen being kicked over by garbage man.

Continuity error: At the end when the camera pans the crew just before their pardon, Scotty wears the rank pin of a Commander. This is despite his being promoted to Captain in Star Trek III - The Search for Spock, being listed in this film's credits as "Captain Montgomery Scott," and wearing Captain's pins in the next film, Star Trek V - The Final Frontier (1989).

Continuity error: When Dr. Taylor drops off Spock at the park, the ignition switch of the Chevy pickup is shown in the "off" position, yet engine idling sound continues and there is no sound of the engine starting up again.

Crew or equipment visible: Just before Spock checks the bus map at a stop, you can see several crew members are visible through a large glass window of a restaurant - one of them even clearly wears a Star Trek IV security badge, and all are wearing walkie-talkies.

Crew or equipment visible: When Sulu accidentally turns on the windshield wipers of the helicopter, the wipers were broken so a grip had to move the wipers manually. Look closely and you can see his finger holding on to the blade as it moves back and forth.

Continuity error: The pizza box Kirk holds after Gillian drops him off at the park is smaller than the pizza they had ordered "to go" in the previous scene. Then, when Kirk beams aboard the ship, the pizza box is gone.

Continuity error: The painted-on "HMS Bounty" on the Bird-of-Prey is visible only when Kirk asks his crew if they will stand trial with him.

Crew or equipment visible: When the Klingon ship is descending towards the whaling ship, there is a shot of the whales immediately following a quick shot of the harpoon. At the extreme right-hand side of the underwater whale shot you can make out a diver from waist up.

Audio/visual unsynchronized: When Scotty is typing on the computer in the plexiglas factory and his hands are shown the sound effects of typing to not match up with his hands, which are moving much slower.

Continuity error: After Kirk rescues Scotty and Gillian, he tells Scotty to close the escape hatch on the bridge; he never does and it is left open.

Plot holes: The whales and water are in the storage tank in the ship, but there is no indication that there is any void space for air in the tank or how the whales would be able to surface and breath in the uncertain G-forces of time travel.

Audio/visual unsynchronized: Immediately after the whales' transponders are located in the Bering Sea, Gillian can be seen to mouth "How did you do that?" without sound, then she is immediately seen and heard giving the same line from another camera angle.

The film opens with a dedication to the crew of the Space Shuttle Challenger.

At the begining of the Australian Home video version (before the dedication to the Challenger crew), a prologue narrated by Kirk and containing scenes for the last two movies brings the viewer up to speed on what's happened. This wasn't included in the cinema release, instead the opening titles were slightly altered.

In the summer of 2002, plans were announced for a special director's edition DVD of this film to be released, following on previous reissues of Star Trek: The Motion Picture and Star Trek: The Wrath of Khan. The new edition is expected to be reedited and possibly include additional footage (as extras on the DVD at least if not in the movie itself).

The film was originally released in 1986, which was the 75th Anniversary of Paramount Studios. Accordingly, the opening logo for the film originally had the 75th Anniversary sign on it, as did the original video release. All subsequent video releases have included the regular Paramount logo.

The German theatrical version contains a short summary of the two previous movies, instead of the challenger-dedication. Later video versions had both the summary and the dedication.