We report on a del(8)(p22) in a severe intrauterine growth retarded newborn with balanced atrioventricular canal defect and prolonged hyperinsulinemic hypoglycemia of infancy. Atrioventricular septal defects are associated with terminal deletions of chromosome 8p. Hyperinsulinism during infancy represents a group of clinically, genetically and morphologically heterogeneous disorders and is also associated with mutations in several genes. However, such 8p deletions are not associated with hyperinsulinemic hypoglycemia of infancy.