Plasma malonyl dialdehyde (MDA) concentration was determined by Placer method in patients with pulmonary tuberculosis before and during treatment period with tuberculostatic drugs. Patients were divided into three groups. Group I comprised 20 patients (10 men and 10 women) aged 24-74 years (mean 48.3 years) with pulmonary tuberculosis BK(+). Group II comprised 20 patients (15 men and 5 women) aged 19-67 years (mean 45.1 years) with pulmonary tuberculosis BK(0). The control group consisted of 16 clinically healthy persons (12 men and 4 women) aged 28-59 years (mean 42.5 years). In patients blood samples (5 ml) were collected for examination from cubital vein before, after 1-month and 2-month treatment period with tuberculostatic drugs. In the control group blood samples were collected from cubital vein once. Results of our study showed that plasma MDA concentrations in patients with pulmonary tuberculosis, both before and during treatment period with tuberculostatic drugs, were significantly higher, in comparison to the control group.