OBJECTIVE: The prognostic value of deoxyribonucleic acid (DNA) ploidy in renal cell carcinoma (RCC) is not well-defined among modern surgical nephrectomy series. We sought to determine which variables correlated with overall survival and recurrence-free survival in the modern era. METHODS: We reviewed all patients from 1992 to 2000, who prospectively had DNA ploidy analysis of their primary tumor determined at the time of nephrectomy for nonmetastatic RCC. Variables examined included age, gender, ethnicity, presentation (incidental vs. symptomatic), preoperative laboratory studies, American Society for Anesthesiology class, tumor size, tumor-nodes-metastasis stage, histology, Fuhrman grade, and diploid versus nondiploid tumor. Statistical analyses of overall survival and recurrence-free survival were performed using the Kaplan-Meier method, log-rank test, and Cox regression model using commercially available software. RESULTS: Sixty men and 41 women, median age 61 years (range, 23-85), were included. Pathologic stage included T1 (54 patients), T2 (14), and T3 (33). Eighty-four patients had conventional RCC. A total of 58 patients had well-differentiated (Fuhrman Grade 1  or Grade 2 ), 28 had moderately differentiated (Grade 3), 12 had poorly differentiated tumors (Grade 4), and 3 were not specified. There were 52 patients who had diploid tumors, and 49 had aneuploid tumors. Median follow-up was 39 months (range, 0-109). Actuarial 5-year overall survival was 70%, and 5-year recurrence-free survival was 76%. Diploid tumors were significantly associated with better recurrence-free survival (P = 0.02) but not overall survival (P = 0.17). On multivariate analysis, the American Society for Anesthesiology class (P = 0.01), abnormal preoperative platelet count (P = 0.03), and tumor differentiation (P = 0.01) were independent predictors of overall survival, whereas only tumor differentiation (P = 0.05) was an independent predictor of recurrence-free survival. CONCLUSIONS: In the modern era, DNA ploidy is not an independent predictor of either overall survival or recurrence-free survival in patients with nonmetastatic RCC. The most important predictor of recurrence-free survival is tumor differentiation.