Dopamine D(2) receptors are implicated in stimulant-induced behavioral sensitization.(7,10) Studies using selective receptor antagonists also implicate the D(4) receptor, a member of the dopamine D(2)-like receptor family.(3) Accordingly, dopamine D(4) and D(2)-like receptor levels in rat forebrain were examined by computed autoradiography after repeated (+)-amphetamine treatment that induced behavioral sensitization. Receptor binding was quantified in critical brain regions including caudate-putamen, nucleus accumbens septi, medial prefrontal cortex and hippocampus. No significant differences in D(4) or D(2)-like receptor levels were detected among rats sensitized to amphetamine, those exposed to amphetamine but killed before behavioral sensitization emerged or vehicle-treated controls. The findings indicate that expression of amphetamine-induced behavioral sensitization is not associated with altered D(4) (or D(2)) receptor density in rat forebrain.