The effects of several concentrations of dopamine on chick optic tectum adenylate cyclase were studied. Dopamine produced a dose-dependent increase in the intracellular content of c-AMP. These effects were specifically antagonized by haloperidol and chlorpromazine, whereas antagonists at alpha-and beta-adrenoceptors were significantly less effective. In conclusion, the present experiments provide evidence for the existence within the avian optic tectum of a dopamine-sensitive adenylate cyclase activity.