IN 1924, just two years after the discovery of insulin by Banting and Best,1 Harris2 published his report on "Hyperinsulinism and Dysinsulinism," having noted in several patients a clinical picture similar to that caused by overdosage of insulin. Nicholls,3 in 1902, first described the finding at autopsy of an islet cell tumor, but the possible clinical significance was not recognized until this syndrome simulating insulin shock was described by Harris. In 1926 Warren4 reviewed 20 cases of islet cell hypertrophy observed at autopsy, in only a few of which were there significant symptoms of hyperinsulinism. According to Bockus,5 an estimated 80 per cent of proved cases of islet cell tumors are clinically silent lesions, giving no symptoms of hyperinsulinism. The first case in which operation was done for an islet tumor was reported by Wilder, Allan, Power and Robertson6 in 1927. An extensive islet