PURPOSE Ablative treatments (cryoablation or radio frequency ablation) for renal cell carcinoma aim to decrease morbidity by treating renal tumors in situ, eliminating the need for extirpation. These technologies have potential for complications previously unassociated with renal tumor treatment. We identified complications associated with percutaneous and laparoscopic ablative treatment of renal tumors. MATERIALS AND METHODS Groups at medical centers with reported experience with ablation of renal tumors were invited to participate in this study. Each group submitted retrospective data regarding overall ablative treatment experience and associated complications. For each incident the nature of the complication, its associated morbidity, the necessity and nature of any subsequent interventions, and the final patient outcome were evaluated. Complications were divided into minor and major categories. Data were collected from groups at 4 institutions with a combined experience of 271 cases. Of these cases 139 were cryoablation and 133 were radio frequency ablation. There were 181 procedures performed percutaneously and 90 performed laparoscopically. RESULTS A total of 30 complications occurred (11.1%) with 5 major (1.8%) and 25 minor (9.2%) complications, and 1 death (0.4%). Overall 26 of the 30 complications (86.7%) were directly attributable to the ablation procedure. The most common complication was pain or paraesthesia at the probe insertion site. CONCLUSIONS Ablation technologies appear to have a low complication profile when used to treat small renal tumors. The majority of complications are minor and require observation only. Further study and followup are necessary to determine long-term oncological efficacy.