Oral atenolol (25, 50 and 100 mg) and placebo administered once daily were tested in a double-masked, randomized cross-over study. Ten patients (18 eyes) who had untreated intraocular pressure (IOP) 22 mm Hg participated. A fall in IOP was observed 2 h after administration, with a mean maximum after 2–5 h. The decrease in IOP was dose-dependent and persisted 24 h during treatment with the higher doses. After 7-day treatment a significant decrease in IOP was still noted 24 h after intake of 50 and 100 mg. The mean maximum decrease in IOP was observed at the same time as on day 1, but the fall in IOP was slightly diminished. During the treatment period a reduction in pulse rate was seen with all the doses tested. A fall in systemic blood pressure was also observed with the higher doses. Two patients reported side effects that could be related to haemodynamic influence.