OBJECTIVE To evaluate the long-term effect of laser trabeculoplasty (LTP) in patients randomized to multi-treatment in the Glaucoma Intensive Treatment Study (GITS). METHODS Patients with untreated newly diagnosed open-angle glaucoma were treated with three intraocular pressure (IOP)-lowering substances for 1 week and then 360° argon or selective LTP was performed. IOP was measured just before LTP and repeatedly during the 60-month study period. Our previous report on 12 months follow-up data revealed no effect of LTP in eyes having an IOP <15 mmHg before the laser treatment. RESULTS Before LTP, the mean IOP ± standard deviation in all 152 study-eyes of 122 multi-treated patients was 14.0 ± 3.5 mmHg. Three eyes of three deceased patients were lost to follow-up during the 60 months. After exclusion of eyes that received increased therapy during follow-up, the IOP was significantly reduced at all visits up to 48 months in eyes with pre-LTP IOP ≥15 mmHg; 2.6 ± 3.1 mmHg at 1 month and 1.7 ± 2.8 mmHg at 48 months, n = 56 and 48, respectively. No significant IOP reduction was seen in eyes with pre-LTP IOP <15 mmHg. Seven eyes, i.e., <13%, with pre-LTP IOP ≥15 mmHg at baseline had required increased IOP-lowering therapy at 48 months. CONCLUSIONS LTP performed in multi-treated patients may provide a useful IOP reduction that is maintained over several years. This was true on a group level when the initial IOP was ≥15 mmHg, but if the pre-laser IOP was lower than that, chances of LTP success were small.