Originally released at 110 min.; re-edited and re-released in a slightly longer version (112 min.) in 1978 when many of its then-unknown stars became famous.
One minor digital effect has been added, at the request of director George Lucas, and can be found on the 1998 Collector's Edition DVD and VHS. In the original theatrical release, when the movie title credit appears on screen in front of Mel's Drive-In, all that is seen behind the diner are buildings and a cloudy/grey sky. On the Collector's Edition DVD and VHS, a sunset with clouds has been digitally added in where the cloudy/grey sky originally was. The original shot used in the film can be seen at the opening of the American Graffiti documentary, which is on the same DVD/VHS.
The 1978 re-release version was re-mixed for Dolby Stereo, which was not available when American Graffiti was produced.
One version has appeared on television with several scenes cut, including the entire sock hop except for the Louie, Louie sequence (which, ironically, was added to the 1978 re-release).
In addition to the Louie, Louie sequence at the hop, the reissued version had two other scenes added to the original release: Terry's exchange at the used car lot just before the first hop sequence, and Bob Falfa singing Some Enchanted Evening from South Pacific after he picks up Laurie. In the original release, John Milner is listed as having been killed by a drunk driver in June of 1964 in the closing segment just before the final credits. When the movie was reedited in 1978, the date of his death was changed to December of 1964, most likely in anticipation of the release of its sequel, More American Graffiti.
Most TV versions include audible dialogue in the scene where Steve and Budda are sitting together inside the drive-in with Laurie looking in through the window. Budda can be heard asking, "Why not?" at one point and, "Hey listen, if you think I'm chasing you again," just before she says, "This time it would be just for fun. OK?" This added dialogue is not present in any of the video releases, nor is it present in the DVD.