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BACKGROUND Nephron-sparing surgery is the preferred surgical management of cT1 renal masses, but observational and randomized data conflict regarding a survival benefit. OBJECTIVE To examine the associations of radical nephrectomy (RN) versus partial nephrectomy (PN) with oncologic and nononcologic outcomes. DESIGN, SETTING, AND PARTICIPANTS A total of 2459 adults were treated with RN or PN between 1990 and 2011 for a unilateral, sporadic, cT1, M0 solid renal mass. INTERVENTION RN or PN. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS Associations of the type of nephrectomy with oncologic outcomes (local ipsilateral recurrence, distant metastases, and cancer-specific mortality [CSM]) and nononcologic outcomes (other-cause mortality [OCM], all-cause mortality [ACM], ≥10% decrease in estimated glomerular filtration rate [CKD10%], and decrease in estimated glomerular filtration rate to <45ml/min/1.73m2 [CKD<45]) were evaluated using several propensity score (PS) techniques. RESULTS AND LIMITATIONS After PS adjustment using preoperative features, RN was associated with an increased risk of distant metastases, CSM, ACM, CKD10%, and CKD<45, but not with OCM. However, there remained imbalance in pathologic features. We therefore repeated these analyses in the subset of 1609 patients with renal cell carcinoma (RCC). After adjusting for both preoperative and pathologic features, there was no significant difference in the development of distant metastases or CSM. Although RN remained associated with an increased risk of CKD10% (hazard ratio [HR] 2.07-2.21; p<0.001 for each PS technique) and CKD<45 (HR 2.70-2.99; p<0.001 for each PS technique), it was not significantly associated with OCM (HR 1.10-1.17; p=0.08-0.5 for each PS technique) or ACM (HR 1.14-1.15; p=0.2-0.3 for each PS technique, except HR 1.18; p=0.03 by inverse probability weights). Limitations include unmeasured confounding. CONCLUSIONS Although RN was associated with an increased risk of chronic kidney disease compared with PN, it was not associated with a statistically significant difference in CSM or ACM among patients with cT1 RCC. PATIENT SUMMARY This study suggests that partial nephrectomy is not associated with markedly improved survival compared with radical nephrectomy.