OBJECTIVE: The goal of this study was to retrospectively evaluate the outcome, including feasibility, safety, diagnostic yield, and factors affecting the success of computed tomography fluoroscopy-guided biopsy when performed during the same procedure than radiofrequency ablation (RFA) in renal tumors strongly suspected of being T1a renal cell carcinoma (RCC). MATERIALS AND METHODS: Nineteen patients (13 men, 6 women; mean age, 66.7 years) with a total of 19 suspected renal tumors (mean diameter, 1.8cm) underwent computed tomography fluoroscopy-guided biopsy during (n=6) or immediately after (n=13) RFA. All patients were strongly suspected of having RCC on the basis of patient's medical histories and/or the results of imaging investigations. All procedures were divided into diagnostic and non-diagnostic biopsies. Various variables were compared between the 2 groups using univariate analysis. RESULTS: In all tumors, biopsy procedures were technically feasible. No major complications were observed, except for 8 minor post-procedural bleedings. All but one tumor was completely ablated. Local recurrence in the ablation zone as well as tumor seeding in retroperitoneal fat occurred in 1 patient 8.5months after the procedure and were successfully treated with further percutaneous cryoablation. Thirteen tumors were diagnosed as RCC, whereas 6 were ultimately found to contain normal renal tissue (n=5) or connective tissue (n=1). Univariate analysis revealed that none of the variables were significantly different between the diagnostic and non-diagnostic biopsies. CONCLUSION: The performance of renal tumor biopsy and RFA in the same session is feasible and safe. Although pre-treatment pathological diagnosis would be generally desirable, simultaneous biopsy with RFA can be an option for the patients who are not amenable to pre-treatment biopsy.