This review evaluated the clinical evidence of the comparative efficacy and safety of bimatoprost and latanoprost in lowering intraocular pressure (IOP) in patients with glaucoma and ocular hypertension. Four head-to-head, randomized, and controlled clinical trials of bimatoprost and latanoprost with treatment periods ranging from 1 to 6 months were identified from searches of the MEDLINE data-base through February 2004. According to a review and comparison of the results, bimatoprost, when compared with latanoprost, was associated with greater mean reductions in IOP, greater mean increases in the percentage of patients demonstrating target IOP, and greater response rates. The differences between drugs were not always statistically significant. Overall, the between-group differences in mean IOP ranged from 0 to 1.5 mm Hg. In 92% of the IOP measurements, the mean IOP was lower among patients given bimatoprost than among those given latanoprost; in the remaining 8%, the IOP reduction was equal. Transient, mild conjunctival hyperemia was the most frequently reported adverse effect associated with either drug, but it occurred more frequently with bimatoprost. Overall, both drugs were well tolerated. As a 1-mm Hg change in IOP has been shown to reduce the risk of progression in patients with glaucoma (according to the Early Manifest Glaucoma Trial), the greater efficacy demonstrated by bimatoprost in lowering IOP may be clinically significant.