A study was made to elucidate the in vitro effects of long-wave laser irradiation on NAD(P)-dependent lymphocytic dehydrogenases in peripheral blood of healthy subjects and patients with fibrous-cavernous tuberculosis of the lungs. In addition to suppression of T-cell immunity and reinforcement of humoral factors, such patients demonstrated predominance of catabolic processes over anabolic, reduction of the substrate flow by Krebs cycle. The above phenomena explain different responses to long-wave laser irradiation (632 nm) in healthy subjects and tuberculous patients who are noticed to develop more active transfer of the lipid catabolism products to glycolysis.