This is a review about the dumping syndrome (DS). It seems that the DS is more common than is acknowledged in normal clinical work. The mechanisms of DS are complex and not fully understood. The patients with DS present disturbances in food passage, digestion, absorption, blood glucose regulation and in metabolism of intestinal peptides and blood circulation. The most useful laboratory testing to detect a patient with DS is the dumping provocation test performed as oral glucose tolerance test in combination with determination of blood hematocrit. The treatment of DS includes first dietary advice, and then when needed supplementation of dietary fiber, guar gum, and use of somatostatin analogue. Operative treatment of DS should be considered when harmful DS prevails despite the nonoperative methods, and especially when it is associated with malnutrition. The selection of the operative method should be tailor-made for each patient. The reconstruction of the pylorus is the most important single operative method. The other methods applied are jejunal segment interposition and Roux-en-Y diversion.