Purpose: We evaluated the effect of oral single-dose (20 mg) ketanserin on intraocular pressure (IOP) in normotensive and hypertensive eyes. Methods: This study included 15 healthy volunteers and 16 patients with ocular hypertension. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, IOP and pupil diameter were recorded at baseline and at 1-hour intervals for 6 h, in addition, tonographic outflow facility was studied at the third hour after the administration of placebo or an oral single dose of 20 mg ketanserin given in a randomized double-blind crossover fashion. The alternative treatment was applied a week later. Results: In both groups, oral single-dose (20 mg) ketanserin significantly lowered IOP and SBP (p < 0.01). No variation was observed in DBP, heart rate and pupil diameter (p > 0.01). Moreover, after drug administration, the total outflow facility measured by conventional tonography increased in a statistically significant way (p < 0.01). Placebo did not induce any significant reduction in IOP and SBP in either group. Conclusion: The results showed that systemic ketanserin can be used in the treatment of glaucoma patients to reduce IOP. Copyright (C) 2001 S. Karger AG, Basel.