Abstract Dopamine (10 −4 M) and vasopressin (1 mU/ml) were found to increase the level of cyclic AMP in the perfusate of rat kidney. There were some differences in the mode of action of these two drugs. Firstly, the effect of dopamine, but not of vasopressin, was completely antagonized by spiroperidol. Secondly, the maximal response was attained within 1 min after dopamine perfusion, but 8 min after vasopressin perfusion. These results suggest that a specific dopamine receptor which acts to increase the concentration of cyclic AMP is located in the vascular tissue of rat kidney.