Summary Angiotensin II was tested for its activity on rabbit aorta, lower esophageal sphincter (LES) from the rat, rat gastric fundus and rat colon. The peptide had a powerful stimulatory effect on vascular and extravascular smooth muscle beginning from concentrations of 10 −10M. Its effect was antagonized by saralasin which acted in the different preparations to approximately the same extent: active concentrations of saralasin varied from 10 −8M to 10 −7M. The activity of angiotensin on the rabbit aorta appeared to be a direct one on its specific receptors. A mixed action connected with stimulation of adrenergic alpha receptors was observed in the rat LES, whereas an interference of the prostaglandin system was pointed out in the rat fundus and the rat colon. The circumstance of a similar sensitivity of the various tissues to the stimulatory effect of angiotensin and a similar degree of antagonism induced by saralasin tends to minimize the hypothesis of different subtypes of angiotensin receptors at least under the conditions of the present investigation.