The purpose of this study is to verify severity of asthma in asthmatic patients through through the arterial blood gas analysis. Subjects were consisted of 103 patients (74 boys and 29 girls), between 2~13 years of ages. Clinically, asthmatic patients were classified into 6 groups, i, e., group 0(no rhonchi), group 1(rhonchi only), group 2(mild attack), group 3(moderate attack), group 4(severe attack), group 5(respiratory failure with disturbance of consciousness). PH kept normal range in the group 0, group 1, group 1 and group 3,but began decrease in the group 4.There was linear fall in Po2 and began decrease in the group 3. HCO3- maintained normal level through the whole range. BE showed acidemia on the whole, and began distinctive decrease in the group 4 and group 5, especially. Hypoxemia, hypercapnia and acidemia were common in patients in severe attacks with disturbance of consciousness.