Robbie Lawler retained his EliteXC middleweight world championship with a second-round knockout victory over Scott Smith in the main event of the "Unfinished Business" mixed martial arts card today at Sacramento, Calif.

Lawler was bleeding from his head after taking an elbow from Smith early in the second round, but responded with knee strikes. After dropping Smith with a knee to the body, Lawler pounced and landed punches to the head.

The referee stopped it 2 minutes, 35 seconds, into the round. It was scheduled for five 5-minute rounds.

Lawler, who is from Iowa, is a former champion of the Hawai'i-based Icon Sport organization.

In other championship bouts, Antonio Silva defeated Justin Eilers by TKO for the heavyweight title, and Jake Shields beat Nick Thompson by choke submission for the welterweight title.

The event was televised nationally on CBS.