The formulation of proper evaluation criteria after superficial bladder cancer therapy poses several methodological problems that are often peculiar to the disease. The Achilles' heel of many trials is possibly found in the criteria used in the evaluation of the trial's outcome. As a consequence, total agreement regarding the criteria for response and the evaluation of response is needed. The adoption of standard response criteria should be given high priority. Uniform criteria of response should be chosen because they meet standards of reliability and statistical validity. Thus, the criteria must be reproducible and correlate with some measures of patient benefit such as quantity and quality of survival. A proposal for standardization in superficial bladder cancer clinical trials is presented based upon the current knowledge of methodology used for conducting clinical trials and upon the experience coming from clinical research groups.