The current TNM staging system for renal cortical tumors (RCTs) differentiates between tumors confined to the kidney (T1, T2) and tumors that extend through the renal capsule and invade into the perinephric fat (T3a). We examined the relative survival rates of patients with T1 and T3a tumors to determine the accuracy of the current TNM staging classification. We analyzed the Columbia University Surgical Urological Oncology Database for all patients with clinically localized Stage T1, T2, and T3a RCTs treated surgically from 1988 to 2004. The primary outcomes included local and distant recurrence. Because the T3a classification is not limited by size, we compared T3a tumors with T1 tumors alone and tumors confined within the renal capsule (Stage T1 and T2 tumors combined). A total of 819 patients underwent partial or radical nephrectomy for RCTs at Columbia University during the study period. After the exclusion criteria were applied, 131 patients with T1N0M0, 19 patients with T2N0M0, and 82 patients with T3aN0M0 conventional renal cell carcinoma were eligible for analysis. The median follow-up was 37 months. The median tumor diameter was 3.2, 3.8, and 5.0 cm for Stage T1, T1 and T2 combined, and T3a lesions, respectively. The estimated 5-year disease-free survival was 95.2% and 90.6% for T1 and T3a RCTs, respectively ( P = 0.922). Patients with Stage T3a tumors experienced similar outcomes as patients with tumors confined to the renal capsule. These data suggest that the T3a classification should be examined more closely to attempt to improve the prognostic validity of the TNM classification.