Altman got his start in TV, directing seasons and episodes of Alfred Hitchcock Presents, U.S. Marshal, Bonanza, Lawman and Route 66, among others. IMDB lists a series of early films prior to and mixed in with Altman's TV work, but only one (The James Dean Story) is at all memorable.

Altman has slowly developed a style of intricate, complex storytelling, involving enormous casts. M*A*S*H was his first big hit, and was supposedly the first R-rated film to use the word "fuck". Altman has developed a following among Hollywood actors, allowing him to pick and choose actors. The Player, arguably his most successful film, is a long, self-referential murder mysterery and a big who's who of cameos. (Check out the extended cast list on IMDB if you haven't seen the film). Short Cuts represents a kind of implosion of his style: it's really long and slow, and while it's still a good movie, it just seems to collapse under its own weight.

Altman has been nominated four times for the Best Director Oscar Award (Short Cuts, The Player, Nashville, MASH), but hasn't won. At Cannes, Altman won a Golden Palm for MASH, and a Best Director award for The Player.

Partial Filmography:

MASH, 1970
McCabe & Mrs. Miller, 1971
The Long Goodbye, 1973
Nashville, 1975
Popeye, 1980
Secret Honor, 1984
Vincent & Theo, 1990
The Player, 1992
Short Cuts, 1993
Prêt-à-Porter, 1994

Source: IMDB