Dr. Barnett: I think few of us would consider that we know enough new about pyloric stenosis to justify presenting an infant with it to a group of this type. However, the patient to be presented had what appears to be a complication of pyloric stenosis, which we had not encountered previously and one which is of both practical and theoretic interest. The patient will be described and the discussion opened by Dr. Fraad. Dr. Lewis Fraad: Infants with congenital hypertrophic stenosis with or without complications continue to fascinate pediatricians, even though the first American cases were reported in 1788. The patient is a boy, the first-born infant of a 21-year-old mother. The pregnancy and delivery were uneventful. The birth weight was 2.5 kg. Upon discharge from the newborn nursery at 6 days of age, occasional regurgitation of feeding was noted. By the age of 3 weeks the infant had gained only 90 gm. Five days prior to admission to the hospital, vomiting became profuse and projectile. One day before admission the infant's skin appeared yellow to the mother. Upon admission to the hospital at the age of 4 weeks, the infant's weight had decreased to 2,360 gm. He appeared dehydrated and markedly jaundiced. The liver was palpated at the costal margin. An olive-shaped mass measuring approximately 2.5 by 1.5 cm was easily palpated in the midepigastric region. The pertinent laboratory findings in the blood at the time of admission were as follows: Hemoglobin, 19.5 gm/100 ml; CO2 content, 37.2 meq/l; chlorides, 79 meq/l; sodium, 142 meq/l; potassium, 3.0 meq/l; bilirubin, 18 mg/100 ml of which 13.1 mg was reported to be of the indirect-reacting variety. Oral feedings were discontinued. With hydration by intravenous fluids, the electrolyte concentrations in the serum returned to normal values but the high value for bilirubin and the jaundice persisted. Identification of the type of bilirubin by paper chromatography revealed that it was all of the indirect variety. Ramstedt pylorotomy and liver biopsy were performed on the third hospital day.