The effect of subtotal pancreatectomy on brain excitability and its neurochemical mechanisms were studied in mice. The results can be listed as follows : 1. Subtotal pancreatectomy decreased brain excitability in mice, as indicated by an elevation of electroshock seizure threshold and shortening of maximal seizure duration. 2. Subtotal pancreatectomy produced alterations in electrolyte concentration in the brain and serum