The hedonic properties of chlordiazepoxide (CDP) were examined using the place conditioning and the taste conditioning paradigms. Following four conditioning trials, CDP (5-20 mg/kg) produced a conditioned place aversion in an "unbiased" paradigm in which the chamber paired with CDP was counterbalanced among two equally preferred chambers. In a "biased" place-conditioning paradigm, CDP (5 and 20 mg/ kg) prevented the dissipation of the natural aversion to the nonpreferred chamber. Finally, although CDP unconditionally potentiated sucrose consumption, it produced a sucrose aversion in the taste reactivity test and sucrose avoidance in the taste avoidance test when the taste conditionally preceded injections of CDP. The pattern of findings suggest that, when novel to rats, CDP is hedonically aversive.