Introduction The rarity of extreme obesity in childhood, and the even greater rarity of hypoventilation secondary to obesity is suggested by the paucity of children with the Pickwickian syndrome previously reported1-3,17(Table 1). The cardiorespiratory syndrome of obesity with polycythemia, arterial unsaturation, somnolence, hypercapnia, and pulmonary hypertension, found in approximately 10% of extremely obese adults, may be fatal if unrecognized, and may be reversible with weight loss. The purpose of this report is to present the course of the first child proved to have alveolar hypoventilation in association with obesity; to consider the causal factors of her hypoventilation; to discuss her carbohydrate metabolism, and to present ventilatory studies on other obese children. Case History A 4½-year-old female was admitted to The Johns Hopkins Hospital for evaluation of extreme obesity, which had been present since the age of 6 months. From the family history it was learned that several cases