Although he never actually appeared in one of the films he is most famous for, Ray Harryhausen's involvement in a movie is instantly recognisable. For over 35 years he was one of the world's leading special-effects artists and his place as the foremost practitioner of his art is unquestioned.

Harryhausen's speciality was in the use of stop-motion techniques. This involved the photographing of tiny articulated models, one frame at a time, while moving the figures in tiny increments in order to generate the illusion of movement. A painstaking and very time-consuming process, Harryhausen completed comparatively few films in his career, but given the eclipse of stop-motion as a technique by the rise of computer-generated imagery, it seems extremely unlike his work will ever be bettered.

Harryhausen was born in Los Angeles in 1920. Fascinated by dinosaurs from an early age, this interest was given a new outlet following a visit as a young boy to his local cinema. King Kong was the feature and Harryhausen was fascinated by the then-mysterious process whereby the film's prehistoric beasts were brought to 'life'. Over the next few years Harryhausen laboured in his family's garage to learn the secrets of animation. His work paid off and when his career was interrupted by the outbreak of the Second World War he was recruited by the Army Film Unit to produce short animations for them.

After the war Harryhausen realised an ambition when he became the apprentice of Kong's special effects animator, Willis O'Brien, on another giant ape movie, Mighty Joe Young (1949). The film was not a hit and Hollywood abandoned the idea of big-budget, effects-driven fantasies for the next three decades.

Harryhausen spent the next thirty years working on low-budget B-pictures with his production partner Charles H Schneer. Throughout the fifties they produced a string of sci-fi films of varying quality: It Came From Beneath The Sea (1955) featured a giant irradiated octopus* terrorising San Francisco, in Earth Vs The Flying Saucers (1956) Washington DC's landmarks take a hammering - a sequence neatly parodied in Mars Attacks!, and in 20 Million Miles to Earth (1957) a fast-growing alien reptile runs amok in Rome. Most influential, though, was The Beast from 20,000 Fathoms (1953) in which a giant dinosaur is revived from hibernation by an atomic blast and attacks New York. This was a particular success in Japan and lead to a virtual remake called Gojira (1954), known abroad as Godzilla, the first in a long line of kaiju eiga (literally 'big monster') or Suitamation Movies.

By 1958 Harryhausen was getting bored with demolishing cities and looked to classical myth and legend for inspiration. For the rest of his career he drew upon Greek and Arab stories, as well as more recent literature, to create a startlingly diverse series of films.

In the late 1950s and early 1960s Harryhausen based The Three Worlds of Gulliver (1959) on Jonathan Swift's Gulliver's Travels and Mysterious Island (1961) on Jules Verne's sequel to 20,000 Leagues Under The Sea. He returned to Verne for 1964's The First Men in the Moon, and followed this with one of his most famous films. One Million Years BC (1966) was a collaboration with British horror specialists Hammer Films. For once Harryhausen's creatures had to compete for the audience's attention with Raquel Welch in a fur bikini. The film was one of Hammer's biggest moneymakers but isn't the purest example of Harryhausen's work - in several sequences photographically enlarged lizards doubled for dinosaurs.

For many years Harryhausen's mentor Willis O'Brien had tried to make a film based on his treatment 'The Valley of Mist', eventually partly-succeeding in the form of 1956's inferiorThe Beast of Hollow Mountain. In 1969 Harryhausen and Schneer released their own version of the same story as a tribute to O'Brien, The Valley of Gwangi. A variation on The Lost World, it concerns a team of rodeo riders who discover a hidden valley in Mexico populated by dinosaurs, capture an allosaurus and bring it back to civilisation - it inevitably escapes. While the story was far from original the film contains some of Harryhausen's most striking sequences, particularly the roping of an animated dinosaur by a team of flesh-and-blood stuntmen.

For many people, though, it is Harryhausen's mythological films that represent him best. The first of these was The Seventh Voyage of Sinbad (1959), featuring dragons, two-headed rocs, cyclopes, and a fighting skeleton - a motif Harryhausen would return to later. The film was successful and fifteen years later Harryhausen returned to the milieu with The Golden Voyage of Sinbad (1974). It fulfilled another of Harryhausen's ambitions and allowed him to animate a centaur, but the film's finest creation was a six-armed, dancing, sword-fighting statue. It was another successful film and three years later the sequel Sinbad and the Eye of the Tiger appeared. The plot was a retread of the first two films and while the animation was not without some spectacular moments it lacked some of the verve of its predecessors.

For many people, Jason and the Argonauts (1963) is Ray Harryhausen's finest film. While the script takes the usual liberties with the source material (usually to suit Harryhausen's own preferences) the animation sequences are classics - the bronze giant Talos, the startling seven-headed hydra, and the battle with no less than seven animated skeletons being the best known. It was confused with the glut of Italian-made sword-and-sandal then being made on its intial release and flopped at the box office, only to be rehabilitated by matinee re-releases and regular appearances on television.

Even so it wasn't until 1981 that Harryhausen made another Greek film. By this time Star Wars had revolutionised cinema and fantasy was popular again. For Clash of the Titans the producers were able to assemble a cast including Laurence Olivier, but once again the special effects dominate the film. While the Medusa is one of Harryhausen's finest creations, there are many disappointing effects and the film is not one of his best.

Harryhausen retired after Clash of the Titans. He was 61 and beginning to grow weary of spending months at a time locked in darkened rooms while the rest of the crew made three more films. He was also a little disillusioned with the way the industry had changed.

His films had inspired a generation of young film-makers, and made cameo appearances in two films by one of them - John Landis' Spies Like Us (1985) and Beverly Hills Cop III (1994). When Mighty Joe Young was remade in 1998, Harryhausen naturally made a cameo appearance. Though stop-motion has been made obsolete by advances in computer technology, Ray Harryhausen and his films still command affection and respect, and will no doubt work their magic for generations to come.