Repeated vomiting in the newborn or young infant may be produced by persistent relaxation of the hiatus esophagus. Twenty-four patients with this condition have been observed during the past five years. Milder variants may occur more often than have been recognized. The syndrome in the majority of patients is produced by a temporary neuro-muscular dysfunction. When some organic defect such as a congenitally short esophagus is the causative factor the condition is more apt to be persistent or to start later in life. The diagnosis is suggested by persistent, otherwise unexplained vomiting which can be alleviated by keeping the patient in an erect position. An absolute diagnosis can be made only by fluoroscopic examination with a barium swallow. The diagnostic change is persistent relaxation of the hiatus esophagus with retrograde filling of the esophagus during inspiration or with increase in intra-abdominal pressure. Therapy is empiric and consists of the use of thickened formulae and of keeping the patient in the erect position, particularly after feedings.