The non-refluxing colon conduit has been offered as a superior alternative to the ileal conduit for long-term supravesical urinary diversion. The main advantage would seem to be that the upper tracts can be protected by the formation of a ureterocolic anastomosis without reflux, thereby preventing the deterioration associated with ileal conduits, which is presumably secondary to reflux and ascending infection. Although a colon operation is potentially more hazardous than a small bowel operation the short-term complication rates are not significantly different. We report 2 cases of stenosis of the ureterocolic anastomosis to emphasize that this serious complication continues to be a potential problem with any procedure of this type. With long-term followup its present incidence in 8 to 10 per cent of the patients may exceed the incidence of conduits with reflux. In our 2 cases severe stenosis of the ureter within the tunnel was encountered at reoperation. Techniques that may help prevent stenosis include preservation of periureteral adventitia, careful formation and closure of the submucosal tunnel, forming an anastomosis free of tension and tapering the ureters, when necessary, adequately but not excessively. Correction of this complication may require lysis of surrounding adhesions, a ureterocolic anastomosis with reflux, transureteroureterostomy, transureteropyelostomy, replacement of the ureter with small bowel or nephroureterectomy.