Argon laser trabeculoplasty was performed on 45 open angle glaucoma patients with three different laser power levels (0.5, 0.7, and 0.9 W). We evaluated the influence of the treatment variables on the postoperative intraocular pressure (IOP) increase. The only statistically significant correlation we found was with the laser power. Most (75% [6/8]) of the serious IOP increases (greater than or equal to 10 mm Hg) were in the high-power group, and the average postoperative IOP increase was also greatest in this group.