A comparison of the ability of all published proposed clinical staging systems to predict time to prostate-specific antigen (PSA) failure after external beam radiation therapy for clinically localized prostate cancer was performed using an independent radiation database. Cox regression multivariable analyses were used to assess the significance of the proposed staging systems to predict time to post-radiation PSA failure in 465 radiation managed patients. Significant staging systems identified using Cox regression were further tested using established comparative estimates to define the most predictive system. Both the Risk Score staging system and the staging system based on the calculated volume of prostate cancer (cV(Ca)) and PSA optimized the prediction of time to post-treatment PSA failure. The cV(Ca)-PSA system, however, provided a more clinically useful stratification of outcome. Many clinical staging systems for prostate cancer have been proposed. A single clinical staging system for patients with localized prostate cancer based on parameters obtained during the routine workup provided a statistically and clinically significant stratification of outcome after external beam radiation therapy.