A variety of neurochemical and anatomical studies have shown that the ventral striatal nucleus accumbens (NAcc) can be divided into a predominantly medial 'shell' and a predominantly lateral 'core'. These accumbens subdivisions are innervated by different cortical regions and project to different anatomical targets. Additionally, recent behavioral observations suggest functional differences between the accumbens shell and core. In order to further examine core and shell function, we measured prepulse inhibition (PPI) of the acoustic startle reflex after electrolytic lesions aimed at the central NAcc, the NAcc shell, the NAcc core, and the adjacent anteroventrolateral striatum. Acoustic startle is the contraction of whole-body musculature in response to a sudden, loud auditory stimulus, and PPI is the inhibition of acoustic startle by a weak auditory 'prepulse' administered 30-500 ms prior to the startling stimulus. Previous work has shown that PPI is regulated by the NAcc, and recent observations suggest that PPI is regulated by different neurochemical interactions in the core and shell. PPI was significantly reduced by electrolytic lesions of the central NAcc, as well as by lesions that predominantly damaged either the NAcc shell or the core. Lesions of the anteroventrolateral striatum and lateral edge of the NAcc core did not significantly alter PPI. These findings suggest that, despite neurochemical differences between the two subregions, PPI is regulated by both the NAcc shell and core.