A long prevesical ureteral defect was bridged by a somewhat modified Boari's operation. The bladder flap appeared too narrow and thick and was therefore unsuitable for the creation of a tube. It was therefore turned upwards and left in the wound as a buried strip with the upper ureteral stump submucosally implanted in the upper end of the flap. During several weeks a tube developed spontaneously from the flap. The late result was satisfactory.