The effects of graded doses of ethyl alcohol on defence behaviour were studied in nine cats: 0.25 g/kg of body weight had a slight but not significant excitatory effect, 0.5 and 1.0 g/kg had no effect and 1.5 g/kg significantly depressed some behavior components. When taking the scores for all the manifestations combined as an index of gross behaviour, 0.25 significantly intensified, 0.5 and 1.0 did not change and 1.5 g alcohol/kg significantly depressed defence. These results are consistent with the expected effects of alcohol on physiological functions in general.