The New York native's acting breakthrough came in 1987 with "Less Than Zero," in which he portrayed Julian Wells, a young cocaine addict in Hollywood.
One of his greatest performances was as Charlie Chapman for which he earned an Oscar nomination.
In the mid to late 1990s Downey was arrested several times on drug-related charges, and he was in and out of rehab.
His guest-star turn on "Ally McBeal" as McBeal's love interest earned him a Golden Globe.
Once clean, Downey's career started to pick up. In recent years, he landed the role of Tony Stark, the lead character in the blockbuster "Iron Man." The sequel is slated for 2010. In 2009, he was nominated as best supporting actor for his role as a white actor trying to portray a black man in the comedy "Tropic Thunder."
Continuing his 2009 streak, Downey will be starring in "The Soloist" opposite Jamie Foxx and as the great detective in "Sherlock Holmes".