Aims: To determine whether the presence of abnormal B‐cell nuclei predicts the existence of a focal or of a diffuse form of persistent neonatal and infantile hyperinsulinaemic hypoglycaemia in a series of 20 infants.

Intra‐operative frozen sections were performed on small specimens from the pancreatic head, isthmus and tail. In 13 cases, abnormal B‐cell nuclei were identified, but even a near‐total pancreatectomy was insufficient to cure some of these patients, in whom no focal lesion was detected. On the other hand, abnormal insular B‐cell nuclei were not found in seven cases; based on the results of selective venous catheterization, a limited resection was performed, sufficient to cure each patient, and a focal adenomatous hyperplasia was found in each resected specimen.

Intra‐operative examination of small pancreatic specimens taken from the different parts of the gland allows one to determine the type of lesion (focal or diffuse) in neonatal onset hyperinsulinaemic hypoglycaemia, and to decide on the most appropriate surgical treatment.