We treated one eye each of ten patients with ocular hypertension with dipivalyl epinephrine (DPE), a congener of epinephrine. Pupil size and intraocular pressure were measured before and at intervals up to 240 minutes after instillation of a single drop of DPE in concentrations from 0.005 to 0.5%. Concentrations of 0.025% DPE and greater significantly reduced IOP, and mydriasis was induced by concentrations of 0.1% DPE or greater. Comcentrations of 0.1% DPE, instilled twice daily for one month, significantly reduced intraocular pressure during diurnal testing on days 2 and 31. No toxic side effects were noted. The DPE produced dose-related increases of cyclic adenosine monophosphate in the aqueous humor of rabbits.