Long-term follow-up findings after argon laser trabeculoplasty are communicated. The coagulation technique employed was that described by Wise and Witter (1979). The circumference of the chamber angle was coagulated over 360 degrees. The indications were chronic open-angle glaucoma, pseudoexfoliation glaucoma, pigmentdispersion glaucoma, glaucoma in aphakia, and glaucoma after ALT or fistulizing surgery with uncontrolled IOP. Glaucoma cases in which IOP exceeded 35 mm Hg were not treated by this method. Therapy was considered successful if a decrease in IOP to below 20 mm Hg was achieved. The difficulties of finding appropriate parameters for the success of glaucoma therapy are discussed. The percentages of normotonic eyes after ALT with a follow-up period of one to four years are reported and compared with results obtained by other authors. After one year, IOP was normal in 89.9% of 881 eyes (chronic open-angle glaucoma 94%, pigment-dispersion glaucoma 91%, pseudoexfoliation glaucoma 86%, glaucoma in aphakia 88%). After two years, it was normal in 72.6% of 237 eyes (chronic open-angle glaucoma 82%, pigment-dispersion glaucoma 50%, pseudoexfoliation glaucoma 53%, glaucoma in aphakia 75%). After three years, it was normal in 60.5% of 76 eyes (chronic open-angle glaucoma 72%, pigment-dispersion glaucoma 25%, pseudoexfoliation glaucoma 37%, glaucoma in aphakia 66%). After four years, it was normal in 95.4% of 128 eyes (chronic open-angle glaucoma 82%, pseudoexfoliation glaucoma 50%). The results of ALT therapy reported by other authors are similar. A decrease in efficiency, initially of 5% to 10% per year, is seen in eyes thus treated, which may necessitate fistulizing surgery.(ABSTRACT TRUNCATED AT 250 WORDS)