U.S. summer hardcourt season.
Agassi, the second seed, has not played since suffering a stunning straight-sets loss to Thailand's Paradorn Srichaphan in the second round at Wimbledon.
The 32-year-old Agassi has won this event twice. Last year he defeated fellow American Pete Sampras in the final. Agassi has won three titles this year, with the most recent coming at the Tennis Masters Series Rome in May, when he won in straight sets
over Germany's Tommy Haas in the final.
Agassi faces Denmark's Kenneth Carlsen in the first round.
Haas is the top seed and takes on 19-year-old qualifier Alex Bogomolov Jr. of the United States. Haas, who is returning to action for the first time since losing in the fourth round at the French Open, is seeking his sixth career title and first
Third-seeded Frenchman Sebastien Grosjean also is playing for the first time since the French Open, where he lost in the quarterfinals to Russian Marat Safin. Grosjean battles American qualifier Jack Brasington.
Fourth-seeded American Andy Roddick continued his mastery of Hyung-Taik Lee on Monday with a 6-7 (5-7), 6-1, 6-2 victory over the Korean. In a rematch of last year's final at Houston, Roddick fired 20 aces to improve to 5-0 lifetime vs. Lee.
Also Monday, Jan-Michael Gambill outlasted Michael Chang, 4-6, 6-2, 7-6 (9-7) in a matchup of unseeded Americans and a rematch of the 2000 final.