Syntheses of several phenothiazine ligands as potential affinity probes for the D1- and D2-dopamine receptors derived from 4-(3-(10-(2-trifluoromethyl)phenothiazinyl)propyl)-1-(2-aminoethyl )-piperazine hydrochloride are described and their interactions with D1- and D2-dopamine receptors of the bovine caudate nucleus have been characterized. The bromoacetylamido-, maleinimido-, and isothiocyanato-derivatives expressed low selectivity and moderate affinity for both categories of dopamine receptors. 4-(3-(10-(2-Trifluoromethyl)phenothiazinyl)propyl)-1-(2- (isothiocyanatobenzoyl)ethyl)-piperazine hydrochloride did not discriminate among the two subclasses of the dopamine receptors, but showed an extremely strong irreversible binding to the D1-receptors and thus is promising as a highly specific affinity ligand for biochemical and pharmacological studies of the D1-dopamine receptors.