Cardiac mensuration by the roentgenological heart volume method was carried out in healthy 302 cases of male and 152 cases of female. RESULTS : 1. Predicted roentgenological heart volume in male is 641.53$pm$9.22ml and 565.97$pm$7.00ml in female, and shows increase with age in the both sexes but no significant influence with body weight. 2. Relative heart volume in male is 397.08$pm$5.21ml/$m^2$ and 379.73$pm$4.87ml/$m^2$ in female, and significant influence with age, height and weight is nelgligible. 3. Roentgenological mensuration of the relative heart volume is considered to be simple and the best method to express the standard of the heart size.