Hyperinsulinism is primarily a disease affecting neo-nates. Unfortunately, many pediatricians still believe that diagnosing it is difficult. Lengthy diagnostic procedures may postpone rapid, proper treatment, which jeopardizes the child's development, and frequently re-sults in mental retardation. Given the striking clinical appearance of neonatal hyperinsulinism, however, little excuse can be made for not diagnosing the condition within 24 hours (Fig. 1). The recent literature contains data relevant to the three treatment objectives and to the natural history of the disorder, both of which are discussed in this review. The potential of molecular biology for pathogenetic studies is also briefly discussed. In his classic studies on the management of this disorder in infancy and childhood, Aynsley-Green [1] sets the three objectives of treatment: 1) to establish the diagnosis as quickly as possible; 2) to identify the cause of hyperinsulinism, with special reference to the defi-nition of a localized adenoma; and 3) to maintain nor-moglycemia while establishing effective therapy. The natural history of the conditions of his 33 patients are summarized in Table 1.