Houston's win increased its Western Conference first-place lead to five points over Real Salt Lake.

All the scoring was in the first half.

Chicago's Brian McBride got the first goal of the match after taking a pass from Cuauhtemoc Blanco.

The Dynamo tied it shortly afterward on a goal by De Rosario, who got free near the net and easily slipped the ball past Fire goalkeeper John Busch.

Mullan scored the game-winner on a shot to the far post in the 39th minute.

Houston is 9-5-8, Chicago 10-7-5.