PREVIOUS studies have shown that substance P (SP) exerts reinforcing effects following injection into the region of the nucleus basalis magnocellularis (NBM) in rats. The aim of the present study was to further characterize this effect by examining its anatomical specificity. Reinforcing effects of SP were assessed following unilateral microinjection into the NBM or into the nearby rostral part of the ventral pallidum (VP), using conditioned place preference as an index for reinforcement. Intracranial injection of SP was performed through small diameter glass micropipettes which allowed precise delivery of SP in minute quantities. A single microinjection of SP (0.2 and 1 ng) into the NBM produced a conditioned place preference, whereas injection of SP into the rostral VP failed to alter the preference behavior. The results confirm that SP has reinforcing effects when administered into the NBM and provide evidence that these effects are brain-site specific.