Once in the filmmaking mindset, and having written teleplays before, Michael Crichton also went for writing screenplays, beginning with Extreme Close-up (1973), also known as Sex Through a Window, and two of his most famous screenplays, Westworld (1973), which he directed himself and beacame a classic, currently rebooted into a TV series; and the script for a medical drama in 1974, which would be filmed, 20 years later, as the pilot episode of the long running TV series ER (1994-2008).
In 1978 two further screenplays were made into films by himself, with Coma, based on Robin Cook's novel, and The First Great Train Robbery, which is the only one which he wrote, directed and was based on one of his own novels. Later he again directed his own screenplays for Looker (1981) and Runaway (1984).
In 1996 he co-wrote the screenplay for Twister.
In 1978 two further screenplays were made into films by himself, with Coma, based on Robin Cook's novel, and The First Great Train Robbery, which is the only one which he wrote, directed and was based on one of his own novels. Later he again directed his own screenplays for Looker (1981) and Runaway (1984).
In 1996 he co-wrote the screenplay for Twister.
Trivia: Exteme Close-up (1973) and Twister (1996), the first and last screenplays he wrote, are also the only ones he did not direct himself.