Aims of this study is to explore the change of the concentration Exhaled Nitric Oxide (eNO) and the relationship between concentration eNO with FEV1 (Forced expiratory volume in 1 second) in the patients affected bronchial asthma. Study was conducted at the Hospital of University Medical Hai Phong on 99 patients affected bronchial asthma having an average age of 40.5 + or - 5.7 (38 females, 61 males) and 99 normal people (52 males, 47 females) with the same age, in period from fevrier 2011 to august 2011. Methods: eNO concentrations measured by the meter NO breath (Bed Font). FEV1 was measured by automatic ventilator design type Analyser ST 250 (Fukuda Sangyo-Japan). Results: Concentration eNO of patients with bronchial asthma is 34.54 + or - 9.16 ppb, that is higher than in normal people (34.54 + or - 9.16 ppb and 15.25 + or - 5.58 ppb
p 0.05) and higher than in patients with COPD (eNO concentrations in patients with COPD were reported in previous studies by the same author is 27.00 + or - 5.61 ppb). Asthma as severity as increasing eNO concentration (30.86 + or - 6.11 ppb
36.63 + or - 7.24 ppb and 42.92 + or - 9.86 ppb
p 0.05). There isn't difference about eNO concentration between men and women, between aged and young people. There is the relationship opposite moderate between eNO concentration and FEV1 in patients with bronchial asthma (r