We have evaluated the incidence of iatrogenic urethral strictures in a prospective study of 125 patients with a diagnosis of initial, superficial bladder tumors (without prior urethral instrumentation) and who were treated with endoscopic surgery. A global incidence of 12% was found after 24 months of follow-up with the strictures detected a mean of 9.5 months after the endoscopic procedure. These patients were divided into two groups. Group 1 was treated using standard transurethral resection (TUR) and group 2 underwent Nd:YAG laser photocoagulation. Both populations of patients underwent cystoscopic controls every 4 months as part of our standard follow-up protocol in bladder tumors. In the group of patients who underwent diathermy using a 24-F sheath (85 patients), the percentage of stenosis was 16.4%. In the patients treated with laser via a 21-F panendoscope (40 patients), the incidence of postoperative urethral stenosis was only 2.5%. We believe that the electrical dispersion generated by the unipolar electric current as well as the caliber of the operating instruments are factors which may influence the development of iatrogenic endoscopic urethral strictures.