Bimatoprost, a prostamide, effectively lowers intraocular pressure (IOP) in patients with open-angle glaucoma and ocular hypertension. In clinical trials, bimatoprost has demonstrated superiority to the beta-adrenergic antagonist timolol and has consistently provided approximately 1-2 mmHg greater mean IOP lowering than the prostaglandin latanoprost. Bimatoprost is more effective than either timolol or latanoprost in allowing patients to reach the low target pressures that best protect the visual field. Patients on bimatoprost therapy achieve low pressures throughout the day and night. Moreover, 1-year trials have shown that the efficacy of bimatoprost is sustained with long-term use. The most common side effects have been conjunctival hyperaemia, graded as trace or mild, and eyelash growth. No safety concerns have arisen in postmarketing surveillance. Bimatoprost appears to be a valuable new agent for glaucoma therapy.