Abstract The “fumarate+ glutamate+ pyruvate” mixture (FGP), currently used to supply energy in isolated tissues, was found to stimulate glucagon release in the in vitro perfused rat pancreas. The stimulation of glucagon release by FGP resembles that induced by arginine, in that it is biphasic and its amplitude inversely related to the environmental glucose concentration. Both glutamate and pyruvate—but not fumarate—seemed to be involved in the stimulation induced by the FGP mixture. The glucagonotropic effect of the FGP mixture suggests that glucagon release is not invariably suppressed by energy-yielding nutrients.