A child with respiratory failure and cor pulmonale secondary to the obesity hypoventilation syndrome (OHS) was found to have abnormal beta-endorphin levels in cerebrospinal fluid (CSF) and serum. A single iv dose of 10 microgram/kg of naloxone early in the course of respiratory failure resulted in dramatic improvement which lasted approximately 3 to 4 h. The patient failed to response to progesterone, and because of deteriorating respiratory status a low-dose continuous infusion of naloxone, 2 microgram/kg.h, was begun and gradually increased to 10 microgram/kg.h, during which time there was a dramatic improvement in respiratory status and clinical condition. After 5 days, naloxone infusion was discontinued and progressive respiratory deterioration recurred. The child died of over-whelming sepsis and disseminated intravascular coagulation.