OBJECTIVE To evaluate contemporary national practice pattern trends in the use of thermal ablation (radiofrequency ablation and cryoablation) in the management of stage I renal cell carcinoma (RCC), and the factors that lead to using thermal ablation (TA) vs partial (PN) or radical nephrectomy (RN) in the United States. METHODS Within the Surveillance, Epidemiology and End Results (SEER) database, we identified subjects with T1-N0M0 RCC treated with either PN, RN, or TA between 2004 and 2007. Proportions, trends, and multivariable logistic regression models tested the predictors of the use of TA. RESULTS In total, 15,145 patients underwent a procedure for an RCC that was organ-confined and <= 7 cm. Of these, 578 underwent TA, 4402 underwent PN, and 10,165 underwent RN. On unadjusted analyses, patients who received TA were more likely to be older, single, have smaller tumor size, be diagnosed in more recent years, and have more unspecified histologic subtype and tumor grade. In multivariable adjusted analyses, single status (P = .02), male gender (P = .01), increasing age (P < .01), year of diagnosis (P < .01), and smaller tumor size (P = .01) were strong independent predictors of TA use compared with surgery (PN or RN). Further adjusted analyses showed no statistical difference in cancer-specific or overall survival between TA vs PN or RN. CONCLUSIONS TA use for stage I RCC increased over a relatively short period and was performed more commonly in patients of older age and with smaller tumor size. Longer follow-up is needed to assess the comparative effectiveness of TA vs surgery. UROLOGY 78: 93-98, 2011. (C) 2011 Elsevier Inc.