The clinical investigations carried out in a 58 years woman complaining of malaise led to the discovery of an hypoglycaemia resulting from a secreting pancreatic insulinoma. In addition, a chronic pancreatitis, an endocrine hyperplasia (possible nesidioblastosis) and a villous adenomatosis of the pancreatic duct were diagnosed on two biopsies. The immunohistological tests performed on the insulinoma showed insulin, calcitonin and gastrin labelled cells. Electron microscopy displayed numerous neurosecretory granules. The peritumoral endocrine hyperplasia contained intermingled B, A and D cells respectively labelled by insulin, glucagon and somatostatin. Following the operation, the patient recovered without recurrence of the hypoglycaemia (three year follow-up). Factors which may explain such a rare pathological association are discussed.