SPONTANEOUS HYPOGLYCEMIA due to large nonpancreatic neoplasms has been recognized since 1930 when it was described by Anderson1and by Doege.2The relationship between these tumors and hypoglycemia still remains obscure. The following case is that of a perirenal hemangiopericytoma associated with symptomatic hypoglycemia. Report of a Case An 18-year-old male was admitted to Holy Family Hospital on the afternoon of Dec 1, 1961. He had been found in bed late that morning, poorly responsive and disoriented. That evening, except for some dizziness and slight headache, he felt well. He was fully aware of his surroundings but did not recall the earlier events of the day, including his trip to the hospital. In November, 1960, an exploratory laparotomy was done for a possible ruptured spleen, but only a contusion of the abdominal wall was found. For eight months prior to his admission he had headaches of increasing frequency,