The decision improved Lewis' record to 41-2-1, but also drew a barrage of boos from the Los Angeles crowd that had been enthusiastically enjoying a hard-hitting and evenly fought battle.
Klitschko had won the first two rounds before the cut opened early in the third round and grew quickly to alarming proportions. The ring doctor said after the fight that the injury's swelling had obscured Klitschko's vision and made him unable to defend himself.
Klitschko denied he had been hurt and demanded a rematch. Lewis said he would consider fighting the 6-foot-7 Ukraine native again, however was noncommittal when asked if he was ready to retire.