We studied the effects of angiotensin II on the level of plasma insulin and on the activity of liver glycogen phosphorylase, during the hyperglycemic response to this polypeptide in rabbits. The activity of liver glycogen phosphorylase increased during the initial stages of hyperglycemia and the peak was observed at 10min after the injection of this polypeptide. However, with the elapse of time, the activity decreased and recovered to the control level. The level of plasma immunoreactive insulin (IRI) was unaffected by angiotensin II during the initial stages at 0-40min and increased, when the level of blood glucose attained the maximum at 60min. Moreover the elevated level continued for 20min. Under such conditions, blood glucose appears to be gradually restored to the control level by the increase in IRI.