The purpose of this study was to further investigate the effects of thiamine deficiency on blood pressure and heart rate in connection with muricide in rats. The rats, maintained on a thiamine-deficient diet, showed mouse-killing response (muricide). The incidence of muricide was 72% on day 30. In this period, marked decreases in body weight, heart rate and blood pressure were observed in thiamine-deficient rats. The changes of body weight and blood pressure were statistically different from pair-fed and control groups. In thiamine-deficient group, blood pressure of thiamine-deficient killer rats was lower than that of thiamine-deficient non-killer rats. It is noteworthy that recovery of bradycardia and hypotension was observed in thiamine-deficient rats after providing them with enough thiamine, but muricide was not recovered. Thus, it is unlikely that there is a direct correlation between muricide and the disturbance of cardiovascular system in thiamine-deficient killer rats. The present findings showed that muricide induced by thiamine deficiency has different physiological bases from the other types of muricide, i.e., olfactory bulb-lesioned muricide.