The ergoline derivatives, bromocriptine, lergotrile and pergolide, are potent dopaminergic agonists. Topically administered doses of lergotrile and pergolide, ranging from 0.001 to 1% applied unilaterally, produced dose and time-related ocular hypotension in rabbits and monkeys. In contrast, bromocriptine produced moderate ocular hypotension in rabbits but not in monkeys. Lergotrile (1%) produced significant mydriasis in rabbits whereas pergolide (0.01 to 0.1%) produced a slight miosis. Lergotrile and pergolide were also effective in suppressing ocular hypertension induced by water loading in rabbits whereas bromocriptine was relatively ineffective. These data demonstrate that topically administered ergoline derivatives can: 1) lower intraocular pressure in rabbits and monkeys, 2) suppress ocular hypertension induced by water loading in rabbits and 3) alter iris function in rabbits, producing either mydriasis or miosis, presumably by activation of adrenoceptors.