Argon laser trabeculoplasty (ALT) was performed on 125 eyes with primary open-angle glaucoma (POAG) and 32 eyes with capsular glaucoma; all eyes were surgical candidates where maximum tolerable medication had failed to control the intraocular pressure (IOP) below 20 mmHg. There were 93 eyes of men and 64 eyes of women, in the age range from 20 to 84 years. Three methods were used: Group 1, 36 eyes treated with about 100 laser shots to the trabecular pigment band over 360 degrees; Group 2, 84 eyes with about 50 shots to the pigment band over 180 degrees; and Group 3, 37 eyes with similar treatment to the anterior part of the trabecular band. The frequency of the initial IOP rise and the maximum postoperative IOP level were in the order of Groups 1, 2 and 3. Other complications, iritis, hemorrhage and peripheral anterior synechiae, were most frequent in Group 1. The success rate of the postoperative IOP control below 20 mmHg with continued medication was analyzed by the life-table method: It was 39 +/- 8% over the period averaging 39 months in Group 1, 66.5 +/- 6% over 17.3 months in Group 2, and 33.7 +/- 15% over 8.1 months in Group 3. The ALT over 180 degrees aimed at the pigment band gave better IOP control with less complications than 360 degrees ALT. The success rate in the eyes of Group 2 was 57 +/- 6% and 94 +/- 6% in POAG and capsular glaucoma, respectively. The IOP distribution after the ALT had a peak at 16-17 mmHg; the IOP was lower than 15 mmHg in about 21% of the eyes. Concurrent IOP measurement and tomography revealed that the IOP reduction after ALT was due largely to a reduction of the outflow resistance in the aqueous outflow channel.