During pulmonary inflammation increased amounts of reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI) are produced as a consequence of phagocyte respiratory burst. One of the manifestations of these free radical-mediated processes is lipid peroxidation (LP). The aim of our study was to assess the concentration of lipid peroxidation products (LPPs), conjugated diens (CD) and malondialdehyde (MDA), in patients with active TB. Forty-two patients were enrolled into the study. Half (group I) had advanced TB and were sputum smear-positive. The remainder (group II) had only small radiographical changes and were sputum smear-negative. Serum concentrations of CD and MDA were measured at days 0, 7, 14 and 28 in group I and day 0 in group TT. We found that in all patients with active TB C-CD (1.0 +/- 0.05A(233)) and C-MDA (2.01 +/- 0.16 nmol dl(-1)) were significantly elevated compared to healthy controls (0.67 +/- 0.03A(233) and 1.36 +/- 0.08 nmol dl(-1), respectively) (P<0.001). The highest levels of LPPs were in patients with advanced TB. These concentrations were stable during the first month of anti-tuberculous therapy. Our data indicated that, as in bacterial pneumonia, LPPs were enhanced in active TB. The levels of LPPs depended on the form of the disease as they were higher in subjects with advanced disease than in those with only small radiographical changes. Further studies are needed to assess the role of antioxidants as adjuvant therapy in patients with pulmonary TB.