One hundred and forty-seven eyes of 107 primary open angle glaucoma (POAG) patients and 39 eyes of 31 capsular glaucoma patients who were followed up for a minimum of 5 years after argon laser trabeculoplasty were reviewed. The mean preoperative intraocular pressure (IOP) was 23.6 mmHg. The follow-up periods ranged from 5 to 13 years with an average of 8.8 years. Using a life-table method, the probability of success was calculated, as defined by IOP at 21 mmHg or lower with same or less preoperative medical regimen, no deterioration of visual field defect and no requirement of filtering surgery. The success rate at 5 postoperative years was 40.3% for the POAG and 65.7% for the capsular glaucoma, and at 10 postoperative years it was 26. 8% for POAG and 26.9% for capsular glaucoma. An analysis using Cox proportional hazard model showed that preoperative lower IOP, male sex and higher age were the significant determinants for success.