A female infant with extralobar lung sequestration (ELS) combined with bilateral hydrothorax and ascites is presented. A 34-year-old para II, pregnant in the 29th gestation week, was referred to hospital because of acute hy-dramnios. Ultrasound examination demonstrated marked hydramnios, together with ascites and bilateral pleural effusion in the fetus. In the amniotic fluid, alfafetoprotein was found normal and the karyotype showed a normal chromosome pattern, 46 xx. The hydramnios was so severe and the cervix so unripe, that cesarean section had to be undertaken, and a girl of 1 650 g, and 42 cm long was born. Just after delivery the infant had bradycardia, cyanosis and respiratory insufficiency, with Apgar score 2 during the first 15 min. Manual ventilation followed by Servo respirator with 100% oxygen was given, but with poor effect. The infant lived only 6 3/4 hours. At autopsy there was hydro-thorax, bilateral collapsed lungs and ascites and ELS as the only congenital malformation.