Hypertrophic stenosis of the pylorus is a disease of the final part of the stomach where the pylorus muscle thickens. The pylorus is narrowed and the passage of contents from the stomach to the small intestine is prevented. It is a common disease in pediatrics, it has been noted that it occurs more often in Western countries and that the incidence has been decreasing in recent years. The etiology is unknown, but it occurs more often in boys, and it is suspected that the main cause is a genetic change. The main symptom is vomiting without admixture of bile, and vomiting becomes more frequent as the disease progresses. The diagnosis is established by radiological processing. In most patients, the thickening is clearly visible on ultrasound, additional diagnostic procedures such as CT and fluoroscopy are rarely needed. After establishing the diagnosis, it is necessary to replace the fluid, restore the electrolyte balance and correct the acid-base status. Treatment is surgical. The approach can be open or laparoscopic. The laparoscopic approach is more common, because recovery is faster, complications are less frequent and the hospital stay is shorter. Intraoperative complications, such as accidental puncture or hemorrhage, are more common than postoperative complications. Remission of the disease has been described only twice so far.