Downey, 35, who was arrested only four months after being released from prison in another drug case, entered innocent pleas to felony possession of cocaine and felony possession of the tranquilizer diazepam, each punishable by up to three years in state prison.
The actor, nominated last week for a Golden Globe for his recurring role on the TV show Ally McBeal, also pleaded innocent to a misdemeanor charge of being under the influence of a controlled substance, which carries a maximum one-year jail sentence.
He also pleaded innocent to a one-year prison enhancement for his prior drug conviction.
The Oscar-nominated star of Chaplin eluded a media throng outside the courthouse 130 miles east of Los Angeles by entering through a side door.
During the brief arraignment before Superior Court Judge B.J. Bjork, Downey let his lawyer, Daniel Brookman, enter the pleas on his behalf.
Downey was asked at one point if he understood his constitutional rights and the actor stood and replied, "Yes, your honor."
There was no drama like a previous appearance in Malibu when he described his drug problems: "It's like I've got a shotgun in my mouth, with my finger on the trigger, and I like the taste of the gun metal," Downey told a judge in 1999.
Another hearing was scheduled for Jan. 29.
The actor was arrested Nov. 25 after an anonymous 911 call led police investigators to a room at Merv Griffin's Resort Hotel and Givenchy Spa. The police allegedly found Downey with cocaine and methamphetamine.
After Downey's arrest, his publicist Alan Nierob said: "He's a recovering addict. Recovering addicts have relapses. He's working hard at his sobriety as he has for the last 18 months."
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