Reality star Stephanie Pratt -- cast member of "The Hills" and sister to Spencer Pratt -- was arrested early Sunday morning on suspicion of drunk driving, ET confirms.

The LAPD confirmed that Stephanie was arrested at 3:45 a.m. in Hollywood and charged with a misdemeanor. "It was your basic DUI. Our traffic officers driving down the street spotted her and pulled her over," Sgt. Sal Ogaz told People.com. "She was cooperative and there were no issues with her arrest."

Stephanie tweeted on Saturday night that she was attending Holly Montag's birthday party at the Los Angeles nightclub Empire. Holly is the sibling to Heidi Montag, sister-in-law to Stephanie. Her tweet read, "It's my sissy @hollymontags b-day party! Just finished dinner and going to Empire but I'm pretty tired, a.k.a. yes, I am the party pooper."