Prior administration of detergents modulates the effects of epinephrine (epi) in isolated, arterially perfused rabbit eyes. Pretreatment with Tween 80, Triton X-100, digitonin and sodium dodecyl sulphate (SDS) caused a dose-dependent reduction of epi induced vasoconstriction of uveal vessels. There also was a dose-dependent reduction of the epi induced fall in intraocular pressure (IOP) after pretreatment with Tween 80 and Triton X-100; digitonin and SDS enhanced the effects of epi on IOP but these effects were not dose-dependent. Significant effects of all four detergents on the efficacy of epi were irreversible. Digitonin probably increased the affinity of epi for the adrenergic receptor as shown by the decrease of the ED50-value; the three other detergents did not significantly affect the affinity. The sequence of administration of epi and detergents is of minor importance for the effects of Tween 80 and Triton X-100 but differs significantly for the effects of digitonin and SDS.