In this study, the tumors of 451 Veterans Affairs patients with prostate cancer were examined. In the biopsy specimens, percentage of tumor and tumor length were observed in addition to Gleason grade. The patients were then followed up until death or for a mean of 4.9 years to see how these measures of the quantity of tumor in the biopsy specimens related to overall survival. Cox proportional hazards model analysis demonstrated that patient age and serum prostate-specific antigen (PSA) level were related significantly to overall survival. After controlling for these 2 variables, percentage of tumor was significantly related to overall survival (P = .0012), and after controlling for age and PSA level, tumor length was significantly related to overall survival (P = .00026). Nevertheless, these 2 measures did not add prognostic information, that is, either one or the other was significant, but not both, probably because they are closely correlated. The results favor including one or the other of these 2 quantitative measures in reports on prostate biopsy specimens with tumor.