Data from 15 infants with persistent hyperinsulinemic hypoglycemia of infancy (PHHI), presented to our hospital from 1976 to 1995, were retrospectively analyzed. Nine patients were successfully managed with prolonged (1.25-13 yr) diazoxide therapy and frequent, low protein feeds. Three of them are still being treated with diazoxide, 7.75, 9.25 and 13 yr post diagnosis. Four patients were managed only with frequent, low protein feeds. One patient had 2/3 pancreatectomy, and another had excision of a focal lesion which proved to be focal nesidioblastosis. Two patients were lost to follow up. No patient has shown neurological damage. One girl developed seizures at age 11.5 yr without hypoglycemia. The patient with 2/3 pancreatectomy developed diabetes mellitus at the age of 20 years. Although conservative management of PHHI is very laborious for the family and the physician, it should be applied as long as euglycemia is accomplished. Definition of the anatomical lesion (focal or diffuse) prior to pancreatectomy is recommended.