IRI, IRG and blood glucose levels after I.V.G.T.T. in normal subjects were not significantly modified when I.V.G.T.T. was repeated during a prolonged calcium infusion (15 mg/Kg body weight per 90'). The Authors advance the hypothesis that no closed relationships exist between serum calcium levels and insulin secretion, in these experimental conditions; with regard to glucagon secretion, further experiences are of course required namely during alpha-cell stimulation.