The two Americans played a tight match that ended with Isner prevailing 6-4, 7-6 (17-15) and moving on to face another Yank, Ryan Sweeting, in the second round.
Also advancing was No. 4 seed Andy Roddick, who eliminated Philipp Petzschner of Germany 4-6, 6-4, 6-1. Roddick was unable to break Petzschner in the first set but got on track in the second set and converted 4-of-6 break chances.
Roddick served nine aces in the match. Petzschner committed seven double faults.
Second seed Marin Cilic of Croatia lost to Jarkko Nieminen of Finland 6-3, 3-6, 6-2. The No. 3 seed, Viktor Troicki of Serbia, was beaten by Steve Darcis of Belgium 6-4, 4-6, 6-4.