OBJECTIVE To evaluate the safety of fixed-combination latanoprost/timolol (Xalacom) in patients requiring additional intraocular pressure (IOP) reduction over 5 years. METHODS This phase 3b, open-label, multicenter study included prostaglandin-naive participants with open-angle glaucoma or ocular hypertension insufficiently responsive to β-blockers and requiring additional IOP reduction. Participants were evaluated at eleven 6-month visits. A masked assessor evaluated iris/eyelash changes at baseline and 12, 36, and 60 months. Increased iris pigmentation incidence was compared with a historic control from a similarly designed study evaluating latanoprost. Ocular and systemic adverse events were recorded. RESULTS Among 828/974 treated participants with assessable iris photographs, 233 (28.1%) developed increased iris pigmentation versus 127/380 (33.4%) in the historic controls. Participants with mixed eye colors exhibited greater susceptibility to overall increased iris pigmentation (85.8% in both studies). In this study, most participants (80.3%) with increased iris pigmentation developed only a weak increase. Eyelash changes were seen in 58.1% of participants and darkening of the eyelids in 5-6%; 14.1% experienced a serious adverse event. Adverse events resulted in treatment withdrawal in 133 (13.7%) participants. Most were nonserious ocular adverse events, about half of them ocular irritation. Only 3 of 13 serious systemic adverse events were considered to be drug related by the investigator. Mean IOP reductions were stable over 5 years. CONCLUSIONS After 5 years, more than 70% of participants treated with fixed-combination latanoprost/timolol had no increased iris pigmentation. The fixed combination is safe and well tolerated for long-term treatment in patients with open-angle glaucoma or ocular hypertension.