159 phakic eyes with chronic open-angle glaucoma were treated by argon laser trabeculoplasty and followed for 5 years. According to our criteria of failure, 31 eyes were failures at 1 year (19%), 47 eyes at 2 years (30%), 66 eyes at 3 years (41%), 77 eyes at 4 years (48%) and 82 eyes at 5 years (52%). In the 77 eyes still controlled at 5 years, the intraocular pressure drop was 6.57 mm Hg and the initial medical treatment could be tapered or stopped in only 33 of the cases (43%). In the 82 failures, there was a greater percentage requiring surgery for pressure control during the first year after laser treatment: 16 trabeculectomies in 31 failures (52%). The initial mean intraocular pressures of 7 failures needing surgery during the first 2 months (27.22 mm Hg) and of the 27 failures needing surgery during the 5 year follow-up (24.41 mm Hg) were higher than the initial mean intraocular pressure of the 77 successful cases (22.67 mm Hg). In the 159 eyes followed for 5 years, 19% (31 eyes) to 6% (5 eyes) new failure cases per year were encountered and the initial good results obtained by argon laser trabeculoplasty persisted for about 5 years in half of the cases.