George Clooney was one of the first on the red carpet and won the first award of the night for best supporting actor in Syriana.
Another early arrival was best supporting actress winner Rachel Weisz.
Keira Knightley missed out on a best actress Oscar for her role as Elizabeth Bennet in Pride and Prejudice.
Brokeback Mountain stars Heath Ledger and Michelle Williams are missed out.
Reese Witherspoon's role as June Carter in Walk the Line however saw her pick up the best actress Oscar.
Actress Amy Adams, who wore a Carolina Herrera dress, said she felt "blessed" to be nominated for a best supporting actress Oscar for her role in Junebug.
Sin City star Jessica Alba is due to present an Oscar during the ceremony at Hollywood's Kodak Theatre.
Crash actor Matt Dillon battled it out with George Clooney, Jake Gyllenhaal, Paul Giamatti and William Hurt for best supporting actor.
Best actress hopeful Felicity Huffman arrived with her husband, actor William H. Macy.
Nicole Kidman was due to present the best supporting actor award.
Charlize Theron was nominated for best actress for her role in North County.
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