OBJECTIVES:To characterize the association between potency and comprehensive sexual function. The accurate assessment of sexual function is critical for the evaluation of outcomes after treatment of prostate cancer. The assessments of potency typically used in this context, however, may be oversimplified. METHODS:CaPSURE is a large, observational database of men with prostate cancer. Participants complete health-related quality-of-life questionnaires, including the University of California, Los Angeles Prostate Cancer Index, every 6 months after treatment. A total of 5135 men completed at least one questionnaire and did not use medications for erectile function. The men were categorized as potent or impotent based on their ability to have erections and/or intercourse in the prior 4 weeks. Using the remaining questions on the Prostate Cancer Index, sexual function and bother scores were calculated for each group. RESULTS:Of the 5135 men, 27.4% were potent. The mean sexual function scores were 56 and 13 for potent and impotent men, respectively (P <0.0001). The corresponding mean bother scores were 62 and 36 (P <0.0001). The function scores ranged from 0 to 100 and 0 to 92 among potent and impotent men, respectively, and bother scores from 0 to 100 in both groups. Function was inversely associated with age in both groups, but bother did not change among potent men and ameliorated among impotent men. Individual Prostate Cancer Index questions correlated with potency to a variable extent. CONCLUSIONS:Although potent and impotent men have divergent sexual function and bother scores after treatment, the wide range of these scores in both groups denotes a complex picture of sexual function. The simple documentation of potency after treatment provides an insufficient measure of sexual health-related quality of life and should be supplemented with more comprehensive measures.