This study is to show applicability of RCG and to determine criteria for its use of normals. Instrumentation for data processing was DAP 500-2(Toshiba, Ltd, Tokyo Japan) RI dilution curves recorded an the right ventricle, the left lung, the left ventricle of 12 normal subjects were analyzed to obtain following parameters, namely interventricular peak to peak time and C(2)/C(1) ratio. 1) intraventricular peak to peak time average: 6.40 ± 1.18 seconds (4.80~8.64) 2) C(2)/C(1) ratio of right ventricle average: 0.45 ± 0.08 seconds (0.30~0.59) 3) C(2)/C(1) ratio of left ventricle average: 0.38 ± 0.09 seconds (0.22 ± 0.51) 4) C(2)/C(1) ratio of left lung average: 0.45 ± 0.08 seconds (0.30~0.55)