Abdominal ultrasonography was performed in a total of 19,933 persons at the health care center of our hospital from April 1987 to March 1991. Among them, 16 persons were diagnosed as having renal cell carcinoma and underwent operation. Renal cell carcinoma was detected in one out of 1245 persons (0.08%) by ultrasonography. Of these 16 persons, 15 were males and one was a female and they ranged in age from 38 to 64 years (average age 50.8 years). The tumors were located in the left kidney in 9 and in the right kidney in 7. Regarding the size of the resected tumors, 7 (44%) belonged to T1 and 9 (56%) to T2 by TNM classification of UICC. The minimum size of the tumors was 1.2 x 1.3 cm. Most of the patients had small renal cell carcinoma and all have survived. Abdominal ultrasonography at the health care center is the most effective method of examination for early diagnosis of renal cell carcinoma.