Although underwater weighing technique has been employed to obtain the standard values of body composition parameters, this is not practical in field surveys or in population studies.Thus, the development of a simplified method to calculate body volume from height and weight alone was attempted, since body volume is used to get density by means of dividing weight by volume, which is further associated with calculation of percent body fat. According to Du Bois's equation for body surface area, the form of the prediction equation of body volume from height and weight was constructed as V=AH^aW^b, where V, H and W were body volume, height and weight, respectively. Constant of A, and exponents of a and b were calculated by least square method. The prediction equations of body volume were developed for young men who were sedentary in earlier pilot study, physically active in the present study, and both of them,respectively. Estimation errors for these equations were calculated, i.e., the standard errors of estimate were around 500 ml, and the arithmetic mean differences between calculated and measured body volume did not exceed one percent when expressed in percent of total body volume. The validity of each prediction equation of body volume was evaluated especially from the viewpoint of applying body volume in the calculation of body composition parameters, and resulted in being effective to estimate percent body fat with considerable accuracy. Out of these equations, V=1.4267W^<1.0611>/H^<0.1323> was most recommended. This was derived from combined subjects consisting of both sedentary and physically active young men, and was thought to be applicable to many cases in spite of physical activities. Moreover, a diagram to read percent body fat from height and weight was suggested using the above equation. This seemed to be available for an easily obtainable index of obesity or leanness based on fat content unlike other body build indices, such as Rohrer's index and others.