Sonography is quite sensitive screeening method for the detection of renal mass lesions, but the specifiencity is relatively low. Authors analized the sonograhic findings of the confirmed 67 cases of renal masses excluding simple cyst for possible differential points between each other. The results were as follows : 1. Among the 67 cases, 44 cases (65.7%) were tumorous lesions and majority were malignant tumors. 2. Iso or hyperechoic lesions are relatively specific finding suggestive of the tumorous lesions. 83.3% of isoechoic lesions and 85.0% of hyeprechoic lesions were tumor. 3. Tumor echogenecity of the renal cell carcinoma was variable. Of the 23 renal cell carcinomas, 10 were isoechoic, 8 were hypoecoic and 5 were hyperechoic lesions. 4. In hypoechoic lesions, findings of acoustic enhancement and wall echo were suggestive of nontumours lesion. 5. There was no direct correlation between echogenecity of the mass and tumor vascularity. 6. IVP findings were not sensitive and nonspecific for renal mass lesions , so ultrasound could be the initial step of diagnostic modality for evaluation of the renal mass.