Cardiac mensuration by radiographic frontal cardiac area method was carried out on 21 patient ductus arteriosus patients, 15 females and 6 males. Formula used in this study is as follows. Increase of frontal carciac area in patent ductus ductus arterisus patients seems to be evident but the degree of the cardiomegaly is variable. Comparing to normal data by Choo and Kim, frontal cardiac area in patent ductus arteriosus patients in this series is increased in 15.9% to 98.1%. After surgical ligation of the ductus arteriosus, significant decrease of the frontal cardiac area is observed and the average is 12.5%.