The observations covered 151 cases of hydronephrosis caused by stricture of the pyelo-ureteral junction. The causes of constriction were in 62 cases accessory vessels, in 49 intrinsic stenosis, in 29 surgical lesions, traumas and inflammatory changes, in 23 adhesions, scars and fibrous bands, in 12 cases abnormal ureteral origin, and in 7 cases other factors. In some patients, urinary outflow was hindered by 2 or more factors. Various surgical methods were used. Control examinations were carried out 1–14 years after operation. It appears from the presented material that in cases of accessory vessels, adhesions, scars and fibrous bands the surgical procedure should be chosen individually, depending on the anatomical situation. In cases of non-complicated hydronephrosis the best results are obtained by the Anderson-Hynes operation, while in others by intubated ureterotomy (Davis).