INTRODUCTION: To present the oncological outcomes in a series of patients with cT1a renal cell carcinoma (RCC) treated with radiofrequency ablation (RFA) and its effect on the glomerular filtration rate (GFR). MATERIALS AND METHODS: Forty-five patients (48 renal units) treated at the Belfast City Hospital, over 4 years. Average age is 61.5 years (range 41-80). Eighteen patients (22 renal units) were included with American Society of Anesthesiologists (ASA) II and III. The rest were ASA I. Average tumor size was 2.63 cm (range 1.2 cm-6 cm). Renal function before and after RFA was recorded by means of the estimated glomerular filtration rate (eGFR) and the changes are presented. Oncological outcomes were established from follow up imaging. A satisfactory response was defined by disappearance or a persistence of non-enhancing lesion of smaller size at follow up. A partial response was defined by a persistent but non-enhancing similar size lesion. A failed response was defined by enlarging or persistently enhancing lesions. RESULTS: Mean follow up was 30.6 months (4-60 months). A good response was found in 33 (74%) patients. A partial response was found in 3 (8%) patients and failed response was identified in 8 (18%) patients. The average reduction in eGFR was 11 mL/min. Two patients had a 50% reduction in their eGFR. No patient required dialysis following treatment. CONCLUSION: RFA presents safe treatment choice for patients with RCC, particularly those that are high risk surgical candidates and those who refuse surgery. Short term results suggest good oncological outcomes and preservation of renal function.