Cardiac mensuration by the rentgenoloical heart volume method was carried out on 225 Korean infants, 111 casesof whom were male, 114 were female. Fomulae used in this study are as follows. Predicted heart volume = K X Broaddiameter X Long diameter X Greatest horizontal depth Relative Heart volume = Predicted heart volume (volume inml)/ Body surface area(Meter squared) The constant K represents the product of an ellipsoid are factor and acorrection factor for magnification of cardiac image. Therefore, K value used in this study in 0.42 for 200cm and150cm of focal film distances in posterior-anterior and lateral views respectively. Body surface area is obtainedby use of Du Bois nomogram. The results were as follows; 1. Predicted heart volume at one month of age is 26.44±2.99cm3 in male, 38.93±2.96cm3 in female and at eleven month of age 99.37±3.96cm3 in male, 100.46cm3 infemale. 2. Relative heart volume at one month of age is 135.84±17.92cm3/m2 in male, 140.00±15.29cm3/m2 and atage of eleven month 240.05±15.98cm3/m2 in male, 236.82±6.25cm3/m2 in female. 3. In comparision with Americanstandard value by Mannheimer, Korean infants show smaller heart volume generally.