Amphetamine, PCP, and MK-801 all produced significant increases in rotational behavior ipsilateral to a unilateral 6-OHDA lesion of the MFB. Only amphetamine and PCP, however, elicited increases in striatal dopamine overflow. The effects of PCP on striatal dopamine were rather modest (approximately 50% increases over baseline at peak effect), whereas its effects on rotational output were quite dramatic. Amphetamine, on the other hand, produced a more robust effect on DA at the same time elevating rotational output more modestly. MK-801 had behavioral effects similar to amphetamine, but did not produce any alterations in striatal DA. Thus, there appears to be a significant dissociation between the effects of these drugs on rotational behavior and their ability to alter striatal DA function. In locomotor activity studies, low doses of haloperidol antagonized the effects of cocaine on locomotor output but not PCP or MK- 801. These findings together suggest that the most modest effects of PCP on DA may not contribute to its behavioral actions.