We investigated the changes of plasma B-type natriuretic peptide (BNP) levels in the pediatric asthma as a representative model of the pediatric obstructive lung disease. In 50 patients with bronchial asthma, the plasma BNP levels were determined at their attacks and convalescent phase. Cardiac function of the patients was simultaneously evaluated by echocardiography. The levels of plasma BNP in the acute phase were significantly elevated compared to those in the convalescent phase(Figure, 30.6±31.2 vs 7.7±6.9 pg/ml, p<0.0001). The left ventricle Tei-indexes in the acute phase presented significantly higher values than in the convalescence phase(0.44±0.26 vs 0.35±0.13, p<0.05). Furthermore, the higher levels of plasma BNP were positively correlated with the asthmatic severity-duration scores (p< 0.0001, r=0.53) and inversely correlated with peripheral oxygen saturation levels (p<0.001 , r=-0.38) in the acute phase. Hypoxia-induced myocardial oxygen demand under asthma attack may contribute to BNP secretion. The plasma BNP levels could be a useful marker of latent cardiac impairment in pediatric patients with asthma attack.