The effects of castration and sex hormones on alcohol preference in animal were investigated. Male and female C57BL/6j mice were used for this experiments. At 3 weeks after birth testectomy or overiectomy was performed and then alcohol preference was observed for a prolonged time. Moreover, alcohol preference before administration of sex hormones was compared with that after administration in castrated mice. In addition, effects of castration on liver ADH activity and body weight were studied. The results were as follows. 1. Both castrated males and females showed a tendency of decrease in alcohol preference throughout the experimental period, especially from 5th to 9th months after birth. 2. Following sex hormones administration, a tendency of increase was seen in alcohol preference which had been decreased by castration in a part of animals. 3. Testectomied-mice showed a tendency of slight increase of liver ADH activity (both mU/g and mU/mouse). Ovariectomied-mice showed no changes of liver ADH activity (both mU/g and mU/mousse). In both castrated males and females increase in body weight was observed.