Safety data from a multicenter, double-masked, randomized clinical trial comparing the three commercially available prostaglandin analogue IOP-lowering medications containing benzalkonium chloride (BAK) were analyzed to investigate a possible relationship between BAK content and incidence of ocular adverse events. Latanoprost 0.005% (Xalatan, Pfizer), which exposes patients to the highest daily BAK dose, was associated with significantly lower rates of both ocular adverse events and study medication-related adverse events compared with bimatoprost 0.03% (Lumigan, Allergan) and travoprost 0.004% (Travatan, Alcon Laboratories).