There is an emerging consensus that retrosplenial and posterior parietal cortex importantly contribute to navigation. Several theories of navigation have argued that these cortical areas, particularly retrosplenial cortex, are involved in path integration. In an effort to characterize the role of retrosplenial cortex in active navigation, the effects of temporary inactivation of retrosplenial cortex on spatial memory performance were evaluated in light and dark testing conditions. Inactivation of retrosplenial cortex selectively resulted in behavioral impairments when animals were tested in darkness. These data support the hypothesis that retrosplenial cortex contributes to navigation in darkness, perhaps by providing mnemonic associations of the visual and nonvisual environment that can be used to correct for cumulative errors that occur during path integration.