Argon laser trabeculoplasty (ALT) was used to treat 237 eyes of 156 presurgical patients with various open-angle glaucomas. Patients with primary open-angle glaucoma formed the largest group; intraocular pressure (IOP) control judged clinically to be adequate was achieved in 77.3% of eyes. Eyes with pseudoexfoliative glaucoma demonstrated the greatest IOP reduction achieving control in 90.7%. Eyes with combined-mechanism glaucoma underwent argon laser iridectomy prior to ALT. One month after ALT the IOP was considered adequate in 70% of eyes. ALT may benefit eyes with low-tension glaucoma, pigmentary glaucoma and aphakic open-angle glaucoma. Treatment failures were frequent in eyes with angle recession and uveitis. Complications included IOP elevation (7.8%) and mild iritis; technique modifications minimized their frequency and intensity. ALT demonstrated an excellent benefit-to-risk ratio. Its effect additive to medications, ALT often permitted a reduction in the medical regimen, but rarely cessation of drug therapy. ALT is recommended as an alternative to drainage surgery.