Timolol maleate, a beta-adrenergic blocking agent, was studied in 30 patients with glaucoma. Significant intraocular pressure lowering was achieved with 0.5% and 1.5% solution of the drug. At seven hours following treatment, the IOP was lowered 50% from the pretreatment pressure with both strengths of timolol. There were no subjective or objective ocular or systemic side effects detected. Visual acuity and pupil response were unchanged from pretreatment levels throughout the study. beta-Adrenergic blocking agents and specifically timolol may be an important breakthrough for the medical management of glaucoma.