Russell Crowe and Halle Berry have won the top accolades at the Screen Actors Guild Awards while Ian McKellen and Helen Mirren took the supporting-actor honours.
Crowe was recognised for his role as delusional math genius John Nash in A Beautiful Mind, a win that could boost his chances to win back-to-back Academy Awards.
Halle Berry won for best actress as the widow of an executed death row inmate who becomes involved with one of her husband's guards in Monster's Ball.
Crowe said: "This is a great job, and I want to encourage every one of you in this room to give everything you can to the story. God bless narrative. God bless originality."
The guild awards provide a good glimpse at how the Oscars might shake out on March 24. In SAG's seven previous awards shows, 11 of 14 lead-acting recipients went on to win Oscars, including last year's best-actress winner, Julia Roberts for Erin Brockovich.
McKellen won for his turn as the noble wizard Gandalf in The Lord of the Rings: The Fellowship of the Ring while Mirren played a coolly efficient housekeeper in Gosford Park.
Ben Kingsley won the award for best actor in a television movie or miniseries for his role as Otto Frank in the drama Anne Frank.
Gosford Park, Robert Altman's combination murder mystery and class-war satire, won for best ensemble film cast.
The West Wing swept the dramatic television awards. Martin Sheen won for best actor and Allison Janney for best actress, while the show's cast won the ensemble acting prize.
Megan Mullally and Sean Hayes of Will & Grace won top acting honours for a comedy TV series. Sex and the City won the cast award for comedy show.