AFI described science fiction as "a genre that marries a scientific or technological premise with imaginative speculation. Whether it's a flying saucer whirling through space or a gleaming city on a distant planet, at the core of all science fiction is the provocative question, "What if...?" Science fiction presents stories and situations that tap our brightest hopes and darkest fears about what might, one day, turn out to be true."

(Winners marked with this icon and ranking number)

1. A.I. ARTIFICIAL INTELLEGENCE, DreamWorks, 2001
2. ALIEN, Twentieth Century-Fox, 1979 (# 7)
3. ALTERED STATES, Warner Bros., 1980
4. THE ANDROMEDA STRAIN, Universal, 1971
5. BACK TO THE FUTURE, Universal, 1985 (# 10)
6. THE BEAST FROM 20,000 FATHOMS, Warner Bros., 1953
7. BLADE RUNNER, Warner Bros., 1982 (# 6)
8. CHILDREN OF MEN, Universal, 2006
9. A CLOCKWORK ORANGE, Warner Bros., 1971 (# 4)
10. CLOSE ENCOUNTERS OF THE THIRD KIND, Columbia, 1977
11. COCOON, Twentieth Century-Fox, 1985
12. CONTACT, Warner Bros., 1997
13. THE DAY THE EARTH STOOD STILL, Twentieth Century-Fox, 1951 (# 5)
14. DESTINATION MOON, Eagle-Lion, 1950
15. E.T. - THE EXTRA TERRESTRIAL, Universal, 1982 (# 3)
16. ESCAPE FROM NEW YORK, AVCO Embassy, 1981
17. ETERNAL SUNSHINE OF THE SPOTLESS MIND, Focus, 2004
18. FANTASTIC VOYAGE, Twentieth Century-Fox, 1966
19. THE FLY, Twentieth Century-Fox, 1986
20. FORBIDDEN PLANET, MGM, 1956
21. FRANKENSTEIN, Universal, 1931
22. THE INCREDIBLE SHRINKING MAN, Universal, 1957
23. INDEPENDENCE DAY, Twentieth Century-Fox, 1996
24. INVASION OF THE BODY SNATCHERS, Allied Artists, 1956 (# 9)
25. THE INVISIBLE MAN, Universal, 1933
26. IT CAME FROM OUTER SPACE, Universal, 1953
27. JURASSIC PARK, Universal, 1993
28. MAD MAX BEYOND THUNDERDOME, Warner Bros., 1985
29. THE MATRIX, Warner Bros., 1999
30. MEN IN BLACK, Columbia, 1997
31. MINORITY REPORT, Twentieth Century-Fox, 2002
32. PLANET OF THE APES, Twentieth Century-Fox, 1968
33. REPO MAN, Universal, 1984
34. ROBOCOP, Orion, 1987
35. ROLLERBALL, United Artists, 1975
36. SILENT RUNNING, Universal, 1972
37. SOYLENT GREEN, MGM, 1973
38. STAR TREK: THE WRATH OF KHAN, Paramount, 1982
39. STAR WARS: EPISODE IV - A NEW HOPE, Twentieth Century-Fox, 1977 (# 2)
40. STARMAN, Columbia, 1984
41. THE STEPFORD WIVES, Columbia, 1975
42. TERMINATOR 2: JUDGMENT DAY, TriStar, 1991 (# 8)
43. THEM!, Warner Bros., 1954
44. THE THING FROM ANOTHER WORLD, RKO, 1951
45. THE TIME MACHINE, MGM, 1960
46. TOTAL RECALL, TriStar, 1990
47. TRON, Disney, 1982
48. 2001: A SPACE ODYSSEY, MGM, 1968 (# 1)
49. THE WAR OF THE WORLDS, Paramount, 1953
50. WESTWORLD, MGM, 1973

Nominees: 22 of the 50 movies contained an alien presence.

Winners:

1. 2001: A Space Odyssey (1968)
2. Star Wars: Episode IV - A New Hope (1977)
3. E.T. - The Extra Terrestrial (1982)
4. A Clockwork Orange (1971)
5. The Day The Earth Stood Still (1951)
6. Blade Runner (1982)
7. Alien (1979)
8. Terminator 2: Judgment Day (1991)
9. Invasion of the Body Snatchers (1956)
10. Back to the Future (1985)

Comments: Eternal Sunshine of the Spotless Mind (2004) was a romantic comedy, for the most part, not Science Fiction. Planet of the Apes (1968) and Close Encounters of the Third Kind (1977) should be in the top 10, as well as The Matrix (1999). E.T. - The Extra-Terrestrial (1982) was more a children's fantasy film, not pure science fiction. Terminator 2: Judgment Day (1991), although it had science-fiction elements, was mostly an action film. Dark City (1998) should have been a nominee. Back to the Future (1985) was a light-hearted comedy for the most part, although it had time-travel/sci-fi elements.