Carteolol, a nonselective beta-antagonist, was administered intra-arterially in perfused cat eyes. Carteolol increased both photopic and scotopic electroretinogram b-wave amplitude dose-dependently and reversibly, but carteolol failed to induce significant changes in the flow rate of perfusate. This study suggests that carteolol may increase selectively the retinal perfusion flow rate, though it did not reflect the total perfusion flow, or carteolol may have an interaction with retinal beta-adrenergic receptors related to the origin of the b-wave. These ideas are supported by carteolol's intrinsic sympathomimetic activity and effects on endothelium of vessels.