The 24-year-old soul diva, who recently entered rehab after years of erratic behavior and canceled concerts, arrived at a central London police station to answer questions relating to the alleged incident, her representatives said.
Police didn't directly confirm that Winehouse was in custody, saying only that a 24-year-old woman was being held on suspicion of assault. British authorities don't usually name suspects until they have been charged.
A man was quoted in tabloid newspapers as saying he was hit by Winehouse when he got in her way while she was playing pool at a bar in the Camden neighborhood. She also allegedly head-butted another man who was trying to hail her a cab in the early hours of Wednesday morning.
Winehouse and her husband, Blake Fielder-Civil, were arrested in the Norwegian city of Bergen in October and held overnight on charges of drug possession. A video of her allegedly smoking crack hit the Internet shortly before she won five Grammys this year for her critically acclaimed album "Back to Black."
She was arrested in London in December on suspicion of attempting to interfere with a court case involving Fielder-Civil, but earlier this year police said prosecutors were no longer pursuing the affair.
Fielder-Civil faces charges of perverting the course of justice stemming from a case in which he is accused of assaulting a barman.
By Raphael Satter