Nonpancreatic fibrogenic tumors producing hypoglycemia are very rare and have been reported in only 11 instances thus far. Several theories have been advanced in explanation of this phenomenon. Some authors thought to have seen structures in the tumor resembling islet cells 1,2; others made the increased utilization of carbohydrates by these huge tumors responsible for the hypoglycemia.3,4 The explanation closest to my physiologic concepts, so far, has been given by August and Hiatt, who attributed to the neoplasms the ability to secrete an agent with insulin activity.5 This explanation, however, seems to be incomplete without the implied assumption that only neurogenic fibrosarcomas are capable of releasing agents with hormone activity or, if I may add, with hormone-activating properties. It is, therefore, permissible to assume that most, or perhaps all, of the hitherto reported fibrogenic neoplasms associated with hypoglycemia were of nervous origin. The morphologic similarity between the two