Several lines of evidence suggest that the enzyme catalase plays an important role in many of the behavioral and reinforcing effects of ethanol, through its putative role in the central production of acetaldehyde. The role of catalase in the acquisition of voluntary ethanol consumption was examined in the present experiments by administering the catalase inhibitor 3-amino-1,2,4-triazole (aminotriazole) during the presentation of an ascending series of concentrations of either ethanol or saccharin-quinine solutions. Aminotriazole (0.5 g/kg) significantly attenuated consumption of both ethanol and saccharin-quinine solutions throughout the acquisition period, and this effect remained during a subsequent maintenance period during which no injections were administered. Drinking did recover, however, when the acquisition procedure was reinstated. These results suggest that the effect of aminotriazole on the consumption of ethanol and saccharin-quinine may be the result of a change in reactivity to taste, or an aversive effect caused by drug administration.