Renomedullary interstitial tumor is a common tumor in the renal medulla, present in 26-41% of consecutive autopsy specimens. However clinically evident case is infrequent because this lesion is usually small (less than 3 mm). We report a case of renomedullary interstitial tumor in a 76-year-old woman. Ultrasonogram incidentally revealed a mass in the left kidney while she visited to the hospital for hypertension and unstable angina. A CT scan showed a 2 cm mass that was not clearly enhanced. MR images showed low signal intensity in both T1 and T2 images. Arteriography demonstrated no neo-vascularity. Those findings showed that this lesion was benign one or hypovascular carcinoma. So Left nephrectomy was performed and histological examination revealed a renomedullary interstitial tumor.