The trabecular meshwork in 334 eyes of 260 patients with medically uncontrolled primary and secondary open-angle glaucoma was treated with the argon laser. The average intraocular pressure reduction obtained was 7.1 mm Hg. Tonographic data showed significant increase in the facility of outflow. Glaucoma surgical intervention was avoided in 87.5% of phakic eyes and in 62.1% of aphakic eyes. Laser trabeculoplasty was found to be effective in primary open-angle glaucoma, pseudoexfoliation glaucoma, pigmentary glaucoma, angle recession glaucoma, glaucoma secondary to uveitis, and in eyes with failed glaucoma surgical procedures. The length of follow-up in this series ranged from one week to 21 months, with an average of five months. The major complication noted was a rise in intraocular pressure following treatment. In one eye, a small central island of vision was lost due to this intraocular pressure elevation. Treating one-half of the angle in each of two treatment sessions separated by a few weeks reduces the degree of this pressure elevation. The glaucoma status of 3% eyes was made worse after treatment with trabeculoplasty.