We have developed a new method of measuring fat volume of the human body, using computed tomographic scanning (CT scan) - no ideal or direct method has been available for this calculation. In our study a human body is divided into 11 cylindrical shapes, ie a head, a chest, an abdomen, both sides of forearms, upper arms, thighs and calves to be subjected to the measurement. Eleven computed tomographic sections were examined at the middle point of each segment to obtain the areas of fat tissue. Volume of each cylindrical segment was calculated by multiplying a cross-sectional area of fat tissue by the height of each part. Then the volume of fat tissue of the whole body was determined by the sum of fat tissue volume of eleven parts (as above). By this method, nine massive obese subjects with 147-188 percent of ideal body weight were found to possess fat tissue occupying 30-63 percent of total body volume. We also found female obese patients had a significantly higher percentage of fat tissue than male obese patients when they had same degree of obesity. In addition to the study above, we examined 18 control and 19 obese subjects and measured subcutaneous fat, muscle plus bone and visceral fat separately by CT scan at the umbilicus level. In obese subjects, increased abdominal fatty mass was mainly due to the accumulation of subcutaneous fat, although substantial increase of visceral fatty mass was demonstrated in a few cases.