The aim of the study was to evaluate in man the dose-effect relationship of ibopamine solution 0.25%, 0.50% and 1% on the pupillary diameter and the pupillary reflex to light stimulus and near vision. A cross-over study was performed in comparison with a placebo and with tropicamide solution 1% in 18 healthy volunteers. The results show that ibopamine 1% determines a marked mydriatic effect. At the doses used, it produces a maximum increase of the pupillary diameter with a dose-effect relationship which does not depart significantly from a straight line. The maximum mydriatic effect of ibopamine 1% is significantly greater than that of tropicamide 1%. The mydriatic effect of ibopamine lasts for about 3 h; that of tropicamide lasts longer. Tropicamide 1% markedly and for a long period inhibits the pupillary reflex both to light and to near vision. The effect of ibopamine 1% on the pupillary reflex to near vision is slight, while on the reflex to light stimulus it is essentially comparable to that of tropicamide.