Urinary tract stone disease has been found to be a later complication associated with the construction of the Kock pouch continent urinary diversion. Of 383 patients who underwent Kock pouch diversion between August 1982 and December 1986 stones developed in the pouch in 64 (16.7%), usually on exposed staples or eroded Marlex used to construct the nipple valves. Stones have recurred in 13 of the 64 patients (22%). Most stones were removed endoscopically with techniques similar to those used for percutaneous stone removal. Risk factors for stone formation include Marlex collar erosion and acute pyelonephritis. Changes in surgical techniques with elimination of the Marlex collar and a reduction in the number of staples have reduced the incidence of this later complication to 10%.