Study on 33 asthma patients and identifying maximum expiring volume per second and medium flow between expiring stage of living volume from 25% to 75% in asthma patients without severe stuffy treated at Bach Mai hospital in 2000. The results: there was no difference of sex in asthma. 24% of patients with childhood asthma; 0.6% of them with asthma over 20 years and 30% of them with asthma from 10 to 20 years. After treatment, medium expiring gaz flow at the middle of expiring stage at 25% to 75% of living volume decreased down 50.8% compared with theory value. 48% of patient with mixture ventilation disorder. 40% of patients with obstructed ventilation disorder, 24% of patients with pheriperal obstructed ventilation disorder