The authors studied the ocular hypotensive effect of 8-hydroxycarteolol, a main metabolite of carteolol in normal human eyes, after topical administration in a double masked randomized study. After instillation of 0.01%, 0.1%, 0.5% and 1% ophthalmic solutions of 8-hydroxycarteolol, statistically significant reduction of intraocular pressure was observed 8 and 24 hours after administration (p less than 0.05). It's maximum reduction of intraocular pressure, 1.6 +/- 0.5 mmHg was produced 24 hours after treatment by 0.1% solution. However, diurnal variation of IOP did not show a statistically significant difference.