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 for the evaluation of the trial outcomes. As a consequence of that, 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 response criteria should be chosen because they meet standards of reliability and statistical validity. Thus, the criteria must be reproducible, and they should correlate with some measures of patient's benefit, such as quantity and quality of survival. A proposal of standardization in superficial bladder cancer clinical trials is presented based upon current knowledge on the methodology for conducting clinical trials and upon the experience coming from major clinical research groups.