Asthmatic patients tend to have increased oxidative stress caused by imbalance between oxidants and antioxidants. Changes in the level of antioxidant enzymes, Cu Zn SOD and GPx may play an important role in the development and progression of asthma. It was hypothesized that asthmatic individuals with higher level of oxidative stress may have greater loss of these enzymes, which would be reflected clinically by development of severe asthma. The abnormalities in redox are magnified in asthmatic airways in response to exacerbating factors (1). In this study we aimed to investigate the role of oxidative stress in asthma by determining serum levels of Cu Zn SOD and GPx in patients with asthma compared to healthy individuals. Furthermore, to find out whether the acute attack or severity of asthma would change the serum levels of these enzymes. Serum Cu Zn SOD and serum GPx concentrations were measured in 96 asthmatic adult patients and 55 healthy control subjects matched for age and sex. The patients were recruited from asthma clinics and wards of two tertiary referral hospitals: Al shaab and Omdurman teaching hospitals in Khartoum State. Guided by the GINA classification of asthma, patients were grouped according to asthma severity to mild and severe and according to existence of symptoms to symptomatic and asymptomatic(2). Serum Cu Zn SOD and serum GPx concentrations were measured in these patient groups. Concentrations of serum were measured using ELIZA kits assay according to instructions of manufacturers. Mean serum GPx was found significantly decreased in patients compared with controls (247.24µ/l in patients and 302.42µ/l in controls and P = 0.001). Mean serum Cu Zn SOD was found lower in cases than controls (86.5µg/l in patients and 87.6µg/l in controls). Mean serum Cu/Zn SOD of mild and severe stable cases was 80.64µg/ml and 98.21µg/ml respectively. Mean serum Cu/Zn SOD in symptomatic and asymptomatic was 84.95µg/ml and 102.78µg/ml respectively. Mean serum Gpx of mild and severe was242.14µg/ml and 258.43µg/ml respectively. Mean serum Gpx in symptomatic and asymptomatic was 213.µg/ml and307.73 µg/ml respectively. These findings revealed oxidative stress exists in asthmatic patients showed by deficiency of the antioxidant enzymes compared to controls. Also, their levels decreased during the acute attack compared to the steady state. Control of oxidative stress at the appropriate time with the proper methods is mandatory for effective management of asthma