The incidence of stones after urinary diversion is variable but considerable. The authors report the case of a patient with a stone of the uretero-sigmoid junction of a Mainz II pouch occurring three years after radical cystectomy for recurrent carcinoma in situ refractory to conservative treatment. The patient was treated by anterograde Holmium:YAG laser flexible ureteroscopy. This clinical case illustrates the role of anterograde flexible ureteroscopy combined with Holmium:YAG laser as a minimally invasive, sale and effective technique for the management of stones in a urinary diversion.