Administration of 0.2 mg of glucagon by intravenous bolus resulted in an increase in plasma renin activity (PRA) in 2 of 5 normal volunteers on their usual diet. Two of the nonresponders subsequently showed a PRA response to glucagon after sodium depletion. A lower dose of glucagon (0.01 mg) had no effect on PRA despite a 31 mg/100 ml rise in blood glucose and peak plasma glucagon of over 2000 pg/ml. In conclusion, glucagon can stimulate PRA but it is not a potent stimulator; its effect may be potentiated by sodium depletion.