OBJECTIVE To study the levels of free oxygen redicals in children with bronchial asthma during an attack and symptom free interval. METHODS Serum Malondiadehyde (MDA) levels were studied in 25 children between the age of 6 years-14 years who presented with an acute attack of bronchial asthma. In each patient, serum MDA levels were measured at the time of admission, 24-48 hours after good response to treatment and after a symptom free interval of 3 weeks. Results were compared with control group. RESULTS In study group serum MDA levels were highest at the time of admission, which decreased significantly at 24-48 hours with treatment. After a 3 weeks symptom free interval serum MDA levels had decreased further but were still higher than healthy control group. CONCLUSIONS Lipid peroxidation is increased in bronchial asthma during an acute attack and symptom free period.