For over 40 years science fiction has provided television with both memorable and forgettable moments. "Doctor Who", "Star Trek", "The Prisoner" and Gerry Anderson's supermarionation puppets have attracted a devoted following who refuse to let their legends fade. Other series, such as "Space Patrol" and "Andromeda", have not been so fortunate, slipping into the twilight zone of archive television. This A-Z guide to four decades of both good and bad science fiction on television has been revised and brought up to date to include recent successes such as "Quantum Leap", "Babylon 5", and the new "Star Trek" offspring, "Next Generation" and "Deep Space Nine".