Bilious vomiting in a newborn is a sign of bowel obstruction and can present with or without abdominal distention. The more proximal the obstruction is, the less distended the abdomen will be. A thorough physical exam followed by plain abdominal films often gives the diagnosis. Dilated loops of bowel or air fluid levels suggest the diagnosis of obstruction. Upper gastrointestinal or contrast enema study is often necessary to make a diagnosis. The causes of bilious vomiting in the newborn are duodenal, jejunoileal, and colonic atresias, meconium ileus, meconium plug, hypoplastic left colon, necrotizing enterocolitis, Hirschsprung disease and malrotation with midgut volvulus. The latter represents a neonatal emergency and prompt diagnosis and treatment are necessary to prevent rapid bowel necrosis.