Introduction: Surgery represents the treatment of choice for localized renal cell neoplasia. Partial nephrectomy (PN) has widened its indications over the past two decades and has shown oncological results equivalent to radical nephrectomy for small tumors. The role of negative surgical margins has been widely debated. Intraoperative fresh frozen section analysis is shown to be unreliable, expensive, time-consuming and not well correlated to final pathology. The goal of the present study was to assess the feasibility of intraoperative ex-vivo ultrasound (US) control of resection margins and its correlation to margin status at definitive pathology in patients undergoing PN.Material and Methods: The study was carried out in our institution from February 2008 to March 2010. Patients undergoing PN for T1-T2 renal tumors were included. Ex vivo US was performed by one single senior radiologist. Considering its availability, not all consecutive eligible patients were included. PN was undertaken in a standardized technique applying the "minimal healthy tissue margin" technique. Once resected, the specimen was kept in a saline solution and ex-vivo US was performed to evaluate the whole tumor pseudocapsule.Results: Twelve patients (five women, age (mean}SD) 65}11 years) were included. Intraoperative ex-vivo US showed negative surgical margin in all cases. US duration ranged from 1 to 4 minutes, with a median time of 1 minute. Definitive histological analysis confirmed the presence of two angiomyolipoma, eight pT1a tumors, of which seven were clear cell carcinoma and one was a type II papillary tumor, one pT1b clear cell carcinoma and one pT2 chromophobe carcinoma (size 2.9}2.3 cm). Final pathology revealed R0 margins.Conclusion: Intraoperative ex-vivo US control of resection margins in patients undergoing PN is feasible, time-efficient and well correlated to definitive pathological examination with regards to margin status.