OBJECTIVE The aim of this work was to study the reduction in intraocular pressure (IOP) after two selective laser trabeculoplasty (SLT) treatments in the same area of the trabecular meshwork (TM) compared to two SLT treatments in two different areas of the TM when the initial SLT treatment has failed. METHODS This was a prospective randomized clinical trial for testing the effect of repeated SLT treatments in reducing IOP. The patients in the study all suffered from primary open-angle or pseudoexfoliation glaucoma. All patients were treated initially with SLT (SLT 1) over 180° in the lower half of the TM. Patients who were chosen for retreatment with SLT (SLT 2) were asked to participate in the study. The patients in the study were randomized to either SLT 2 in the same, already-treated TM area or to SLT 2 in the upper untreated TM area. The IOP was measured before and 2 h, 1 month, 3 months, and 6 months after the SLT 2 treatment. Patients who changed medical therapy regimens during this time were excluded. RESULTS A total of 40 patients were included in both groups. At baseline, there were no significant differences between the groups in regards to age (t-test, p = 0.44), gender (χ(2), p = 0.14), pseudoexfoliation glaucoma (χ(2), p = 0.07), time between SLT 1 and SLT 2 (t-test, p = 0.78), IOP before SLT 1 (t-test, p = 0.78), or IOP before SLT 2 (t-test, p = 0.32). At the conclusion of the study, there were no significant differences in IOP between the groups 2 h (t-test, p = 0.65), 1 month (t-test, p = 0.60), 3 months (t-test, p = 0.42), or 6 months (t-test, p = 0.66) after the SLT 2 treatment. CONCLUSIONS Two SLT treatments of the same TM area do not have a significant effect on IOP compared to two SLT treatments in two different areas.