Traboxopine (EGYT-2509) revealed specific dopamine-antagonistic activity with potentially minimal undesirable side effects. EGYT-2509 behaved as a dopamine receptor antagonist in all functional in vitro biochemical-pharmacological tests (striatal adenylate cyclase, striatal dopamine release, prolactin release from pituitary). The drug exhibited a marked preference for adenylate cyclase-coupled (D1) dopamine receptors, followed by the 3H-spiperone displacing potency at striatal receptors. Traboxopine exerts pharmacological and biochemical effects that seem to be partially similar to those of traditional neuroleptics, except for some undesirable side effects (e.g. cataleptogenic, influencing prolactin level). Traboxopine proved to be diversely influential on the dopaminergic components of the integration of sympathetic output and somato-autonomic reflexes. The apomorphine-induced stereotypy was potentiated by lower, and antagonized by higher doses of EGYT-2509. The in vitro potency of EGYT-2509 to block dopamine-mediated inhibition of prolactin release was weaker by three orders of magnitude than that of haloperidol.