4g of l-arginine monochrolide was injected intravenously as a 2-min “pulse” in seven normal subjects. The arginine pulse was given 3 times at a 30 min-interval. Blood was withdrawn from antecubital vein into heparinized disposable plastic syringes at intervals of 3-10 min. Plasma insulin was measured by the double antibody immunoprecipitation technique of Hales and Randle. Plasma glucagon was determined by the radioimmunoassay method of Sakurai and Imura, utilizing antiserum 30K. The 2 min arginine pulses repeated three times at a 30-min interval elicited similar plasma glucagon responses: peak plasma glucagon levels following the first, second and third pulses were 252-458pg/ml, 240-493pg/mland 256-456pg/ml, respectively. The peak plasma insulin levels after the first, second and third arginine pulses were 30-65 μU/ml, 28-58 μU/ml and 24-62 μU/ml, respectively which were not significantly different from each other. All peaks of plasma glucagon and insulin occurred within 3-5 min after arginine injection. Blood glucose rose slightly and transiently after each arginine pulse. These results indicate that the arginine pulses evoke similar insulin and glucagon responses which given at a 30 min-interval, therefore, arginine injection method is a useful tool as the glucagon secretion test.