A pilot study evaluated both the safety and the effect on intraocular pressure control of argon laser trabeculoplasty (ALT) in eyes with secondary forms of open-angle glaucoma. All patients included in this study had poor IOP control and were considered surgical candidates. The ALT was considered successful if IOP control was sufficient to avoid conventional filtration surgery. Fifty-five eyes of 46 patients were treated. The mean follow-up was 8 +/- 4 months. The mean IOP decrease was 13 +/- 9 mm Hg. The ALT caused serious complications in none of the 55 eyes and seemed most effective in treating pigmentary, pseudoexfoliation, and angle-closure glaucoma present after iridotomy. The ALT had minimal therapeutic effect in eyes with uveitic, angle-recession, and congenital glaucoma.