Norepinephrine dipivalylate, a prodrug analog of the catecholamine mediator norepinephrine, was given to 12 ocular hypertensive patients. Single instillations of four concentrations, 0.05%, 0.1%, 0.25%, and 0.5%, were administered weekly to one eye only with the fellow eye receiving a placebo. Intraocular pressure, pupil size, ocular signs, subjective symptoms, heart rate, and blood pressure were monitored at 2, 4, 6, 8, and 12 hours following instillation. An intraocular pressure reduction dose response was seen. After a slow (four-hour) onset of activity, the 0.5% concentration produced clinically acceptable (less than 22 mm Hg) tensions at the 6-, 8-, and 12-hour observations which were significantly (p less than 0.05, paired t test) lower than placebo-control eyes. No clinically important side effects were seen.