The R&B star is under investigation for domestic violence felony battery.
According to LA Police, Brown and a woman were driving early this morning when they started arguing.
After Brown stopped the car, police say the two got out and the fight escalated.
Someone called 911, and officers at the scene say the woman, who was "visibly injured," named the 19-year-old Brown as her attacker.
He'd left by the time police arrived.
Brown's girlfriend, singer Rihanna, was scheduled to perform at tonight's Grammy Awards show but pulled out at the last minute.
Both singers were nominated for Grammys at tonight's' awards.
According to People Magazine, Rihanna and Brown attended a Pre-Grammy party Saturday night.