It is thought to be reliable roentgenologic sign of pulmonary plethora that the diameter of anterior segmental artery(d-ASA) is larger than that of anterior segmental bronchus(d-ASB). To evaluate the reliability of this sign, we compared d-ASA with d-ASB on chest rentgenograms of 100 normal adults. Of the total 105 cases. d-ASA was larger than d-ASB in 40 cases (38.1%), smaller than d-ASB in 34 cases(32.4%) and equal to (d-ASA and) d-ASB in 31 cases(29.5%). The ratio(ABR) and difference between d-ASA and d-ASB ranged from 0.70 to 1.58(mean, 1.05±0.30) and from -1.85mm to +2.45mm(mean of absolute value, 0.75mm±0.57). These results showed that the relationships between d-ASA and d-ASB were variable. Conclusively, d-ASA may be larger than d-ASB in even normal adults and mild degree of pulmonary plethora cannot exectly evaluated with this findings only.