We report two cases of infants who presented seizures and persistent hypoglycemia. In both infants, we established diagnosis of persistent hypoglycemia by hyperinsulinism (PHH); glycemic/insulinic ratio was > 0.3, and we found no pancreatic changes by means of other diagnostic procedures. The medical treatment consisted of hydrocortisone, diazoxide, and octreotide without response. Definitive treatment made was sub-total pancreatectomy; postoperatory evolution was satisfactory, and the histologic report showed changes in Langerhans islet of nesidioblastosis. We conclude that PHH and glucose/insulin ratio > 0.3 indicates that surgical treatment with pancreatectomy should not be delayed.