In order to evaluate the relationship between the ultrasonic image of a kidney and the renal function, we tried quantifying the ultrasonic finding by the following method. The whole kidney are (W) and its central echo complex area (C) on the longitudinal ultrasonic image were measured, and the C/W ratio was calculated in 111 cases. The increased C/W ratio tended to reflect the disturbance of the renal function. It was significantly correlated with serum creatinine and Ccr. In conclusion, the increased C/W ratio probably suggests the disturbance of the renal function and the increased pathological change.