The long-term intraocular pressure (IOP) lowering effect of a beta-adrenergic blocking agent, timolol maleate, in topical administration was compared with the effect of pilocarpine on simple and capsular glaucoma by means of diurnal pressure curves during a six-month follow-up. In simple glaucoma timolol was more effective than pilocarpine in lowering IOP. In the follow-up a significant but not marked increase of the IOP was observed. In capsular glaucoma timolol was not effective enough, but when it was co-administered with miotics the IOP lowering effect was better than with either substance alone. Timolol induced no accomodative myopia, miosis, reduction of tear flow or other side effects. It increased the outflow facility in simple glaucoma but not in capsular glaucoma. During the trial, the anterior chamber depth increased while the corneal thickness remained unchanged. Four out of the six eyes included in a previous report of secondary glaucoma due to chronic uveitis are still, after one year of therapy, controlled with timolol.