The purpose of this study is to review our institution's ten-year experience with imaging surveillance following percutaneous radiofrequency ablation for spontaneous stage T1a renal cell carcinoma, and apply risk stratification based upon the post-procedure CT scan, modified renal nephrometry score, and tumor histology. All renal radiofrequency ablation procedures performed at our institution from 1/1/2005 through 7/31/2015 were reviewed, including pathology and follow-up imaging. Inclusion criteria were all cases of T1a biopsy-proven renal cell carcinoma with at least one follow-up imaging study after the post-ablation scan. Exclusion criteria were benign or indeterminate pathology, Von Hippel Lindau syndrome (VHL), no imaging follow-up available, prior thermal ablation on the same lesion, or RFA discontinued due to technical factors. Cases meeting inclusion criteria were evaluated with mRENAL Nephrometry score, tumor histology, and post-therapy CT scan. Time lag to detection was calculated for each instance of recurrence. 52 cases (in 49 patients) of T1a biopsy-proven renal cell carcinoma status post radiofrequency ablation with at least one follow-up imaging study met the criteria for inclusion. 7 cases of RCC recurrence were identified. Cases of disease recurrence had a statistically significantly higher mRENAL score (7.3 versus 6.0, two-tailed T-test p-value .0087). Recurrence was more likely in tumors with clear cell histology (5/18 versus 2/34 for other histology, Fisher exact test statistic value .0409). There were no cases of disease recurrence if the post-therapy CT scan was definitively negative. The mRENAL Nephrometry score, tumor histology, and post-therapy CT scan inform the rate of tumor recurrence following radiofrequency ablation of T1a renal cell carcinoma. These data may be incorporated into the development of surveillance strategies to yield cost savings and decrease patient radiation exposure, while maintaining surveillance effectiveness.Tabled 1Imaging Surveillance Following Radiofrequency Ablation of Renal Cell CarcinomaCharacteristics of RCC RecurrenceCase#Tumor size (cm)mRENAL scoreRCC histologyPost-RFA CTRFA to detection (days)Lag to detection (days)Size at detection (cm)Recurrence strategy13.58Clear cellIndeterminate11382433.5Surveillance23.18Clear cellNot performed76763.2Nephrectomy32.97Clear cellNot performed4584060.9Repeat RFA43.19Clear cellIndeterminate2382381.7Surveillance52.57Clear cellPositive110.3Surveillance62.77RCC NOSNot performed1861861.9Repeat RFA72.14PapillaryNot performed2712711.6Surveillance Open table in a new tab