Specific binding of [3H]dopamine to membranes from the corpus striatum of rat and calf brain appears to involve the postsynaptic dopamine receptor. Specific [3H]dopamine binding is saturable, wnd with half-maximal binding in calf membranes at 7 nM. Apomorphine is about twice as potent as dopamine in competing for binding sites, whereas (-)norepinephrine is 5% as potent as dopamine and isoproterenol is virtually inactive. The relative potencies of phenothiazines as inhibitors of specific dopamine binding correlates with their clinical potencies and actions on the dopamine-sensitive adenylate cyclase.