To assess the role of peripheral structures of the sympathetic nervous system in the effects of dopamine and dobutamine on some functions of the cardiovascular system, experiments were carried out on anesthetized rabbits in which the blood flow in calf muscles was measured, during rest and during evoked twitches, using the method of 133Xe clearance. The arterial blood pressure and ECG were simultaneously recorded. A complete reversal of the action of dopamine on the arterial blood pressure and heart rate, after sympathetic nerve endings blockade, indicates an important role for the undisturbed neurotransmission in revealing hypotensive properties of this amine. In the action of dobutamine on blood pressure, heart rate and muscle blood flow, the blockade of peripheral structures of the sympathetic nervous system is of minor importance.