<正> The measurement of the right ventricle is carried out on a left lateralchest film.3 points are determined:A is the apex of the sternal angle;B is thetopmost point of the contact surface between the anterior cardiac border and theanterior chest wall;and C is the apex of the anterior costophrenic angle.Thelength of the lines AC and BC is measured.The ratio of BC:AC is considered asan index of the size of the right ventricle.On the basis of the measurements on120 normal subjects

0.54（0.46+2×0.04）is employed as the upper limit of thenormal.A left lateral chest radiogram is very easy to take.The procedure ofmeasurement is simple.An application of this method on the surgically provedcases verified its reliability.In the evaluation of the size changes of the rightventricle

the digital index provides the doctors with a quantitative comparisonmethod.It is helpful in the analysis of serial radiograms.Furthermore

leftlateral chest film will become more useful in assessing the heart size.