The gastrointestinal series of 10 patients with persistent vomiting following pyloromyotomies for pyloric stenosis were reviewed. Four patients had incomplete pyloromyotomies and required reoperation. Their studies showed persistent obstruction with elongation and narrowing of the pyloric channel similar to preoperative studies, except that the proximal muscle mass was tapered in 3 of the 4 patients. Six patients with similar histories of postpyloromyotomy vomiting but who did not require repeat surgery had irregular but much wider pyloric channels, good gastric emptying, and gastroesophageal reflux.