Meryl Streep and Sean Penn were the major winners at the Screen Actors Guild (SAG) awards on Sunday evening.
Mamma Mia! star Streep was named best actress for Doubt while Penn bounced back from disappointment at the Golden Globes to claim the best actor prize for Milk.
"I didn't even buy a dress," Streep joked as she accepted the award. "I'm really, really shocked."
She went on: "There is no such thing as the best actress. There is no such thing as the greatest living actress. I am in a position where I have secret information that I know this to be true.
"I am so in awe of the work of the women this year nominated, not nominated so proud of us girls. Everybody wins when we get parts like this."
Though she missed out in the best actress category, Kate Winslet repeated one of her Golden Globe wins by being named best supporting actress for The Reader - she is up for the best actress Oscar for Stephen Daldry's Holocaust drama.
Golden Globe winner Slumdog Millionaire, which claimed the top prize at the Producers Guild of America (PGA) awards this weekend, continued its march towards Oscar glory by taking the best ensemble cast award at the SAG ceremony in Los Angeles.
And Heath Ledger claimed another posthumous best supporting actor win for The Dark Knight, with cast member Gary Oldman accepting the late Australian's prize on his behalf.
"I'm quite emotional," Oldman said. "He was an extraordinary young man with an extraordinary talent, and it is wonderful that you have acknowledged that."
Winners in the television categories included Alec Baldwin for 30 Rock, Sally Field for Brothers and Sisters and British actor Hugh Laurie, who claimed the best actor in a drama prize for the second year running.
"I actually had $100 on James Spader [winning]," Laurie quipped as he accepted the prize. "This is just not my night!"
Best Actor Motion Picture Drama
Richard Jenkins, The Visitor
Frank Langella, Frost/Nixon
WINNER Sean Penn, Milk
Brad Pitt, The Curious Case of Benjamin Button
Mickey Rourke, The Wrestler
Best Actress Motion Picture Drama
Anne Hathaway, Rachel Getting Married
Angelina Jolie, Changeling
Melissa Leo, Frozen River
WINNER Meryl Streep, Doubt
Kate Winslet, Revolutionary Road
Best Supporting Actor
Josh Brolin, Milk
Robert Downey Jr., Tropic Thunder
Philip Seymour Hoffman, Doubt
WINNER Heath Ledger, The Dark Knight
Dev Patel, Slumdog Millionaire
Best Supporting Actress
Amy Adams, Doubt
Penelope Cruz, Vicky Cristina Barcelona
Viola Davis, Doubt
Taraji Henson, The Curious Case of Benjamin Button
WINNER Kate Winslet, The Reader
Outstanding Performance by a Cast in a Motion Picture
The Curious Case of Benjamin Button
WINNER Slumdog Millionaire
TVBest Actor in a Television Series Drama
Michael C Hall, Dexter
Jon Hamm, Mad Men
WINNER Hugh Laurie, House
William Shatner, Boston Legal
James Spader, Boston Legal
Best Actress in a Television Series Drama
WINNER Sally Field, Brothers & Sisters
Mariska Hargitay, Law & Order: Special Victims Unit
Holly Hunter, Saving Grace
Elisabeth Moss, Mad Men
Kyra Sedgwick, The Closer
Best Actor in a Television Series Comedy
WINNER Alec Baldwin, 30 Rock
Steve Carell, The Office
David Duchovny, Californication
Jeremy Piven, Entourage
Tony Shalhoub, Monk
Best Actress in a Television Series Comedy
Christina Applegate, Samantha Who?
America Ferrera, Ugly Betty
WINNER Tina Fey, 30 Rock
Mary-Louise Parker, Weeds
Tracey Ullman, Tracey Ullman's State of the Union
Outstanding Performance by an Ensemble in a Drama Series
WINNER Mad Men
Outstanding Performance by an Ensemble in a Comedy Series
WINNER 30 Rock