The results of reconstruction of the pylorus in 12 patients with disabling diarrhoea and/or dumping after vagotomy and pyloroplasty are reported. Eight patients, primarily operated on with a truncal vagotomy and pyloroplasty, all indicated frequent diarrhoea as their principal symptom. After the reconstruction operation the stools were normalized in five, and the frequency of diarrhoea was reduced considerably in two patients. Three of four patients who had had a selective vagotomy and pyloroplasty complained of severe dumping after all kinds of food; after the reconstruction these symptoms were milder and provoked by sweets and milk only. The fourth patient with heavy diarrhoea as the principal symptom had postoperatively a slight reduction of the frequency. The operation is easy to perform, and no complication was encountered. The pathogenesis of the symptoms is discussed, and it is recommended that patients with disabling diarrhoea and/or dumping after vagotomy and pyloroplasty undergo a reconstruction of the pylorus.