Estrous hamsters secrete an odorous vaginal discharge that intact male hamsters investigate vigorously during copulatory behavior. Castrated animals are not attracted to this vaginal discharge. In this study we observed that repeated exposure of intact and castrated hamsters to this vaginal discharge reliably produced habituation of investigatory behavior. Presentation of the odor from a novel female to a habituated male caused an increase in investigation (dishabituation). Castration produced a decrease in investigation within 1 week of surgery. However, the surgery did not produce a decrease in dishabituation until 3 months afterward. Testosterone treatment increased chemosensory investigation in castrated animals. It seems likely that the dishabituation observed in this study may represent a sensory component of the Coolidge Effect.