Purpose: The usefulness of prostate specific antigen density for predicting pathological stage and biochemical recurrence after radical prostatectomy has not been well defined. We investigated whether prostate specific antigen density yielded an advantage over total prostate specific antigen for predicting adverse pathological characteristics and disease recurrence following radical prostatectomy. Materials and Methods: A total of 13,434 men who underwent radical prostatectomy for clinically localized prostate cancer between 1984 and 2006 were included in this study. The study population was stratified by Gleason score (6 or less, 7, and 8 or greater), and the clinical and pathological characteristics of each group were compared. We constructed ROC curves and determined the ROC AUC and concordance index to specifically investigate the accuracy of prostate specific antigen and prostate specific antigen density for predicting pathological stage and biochemical recurrence. Results: Prostate specific antigen density was better than prostate specific antigen for predicting extraprostatic extension and biochemical-free recurrence in patients with a biopsy Gleason score of 6 or less (each p <0.001). In patients with a biopsy Gleason score of 7 prostate specific antigen was more predictive than prostate specific antigen density for seminal vesicle involvement (p <0.001), lymph node involvement (p = 0.017) and biochemical-free recurrence (p <0.001). In men with a biopsy Gleason score of 8 or greater there was no statistical difference between prostate specific antigen and prostate specific antigen density in terms of prognostic value for pathological or clinical outcomes. Conclusions: Prostate specific antigen density is highly associated with pathological stage and biochemical-free survival following radical prostatectomy. In lower grade prostate cancers prostate specific antigen density is significantly more accurate for predicting extraprostatic extension and biochemical-free recurrence compared to total prostate specific antigen. It should be considered when counseling patients on outcomes following radical prostatectomy. © 2008 American Urological Association.