Novel approach is suggested to study interferon (IFN) system state in various immunopathological disorders. It is based upon measurement of IFN-alpha and/or IFN-gamma production by leukocytes primed with IFN-alpha or IFN-gamma respectively. Study of IFN-status parameters revealed a tendency to decrease in the induced IFN-alpha production in patients with secondary immune deficiency (SID), autoimmune syndrome (AIS), allergic diseases, lymphoadenopathy (LAP), chronic bronchitis (CB) and bronchial asthma (BAS). Production of the induced IFN-gamma was significantly depressed in all groups except LAP. In priming conditions production of IFN-alpha by leukocytes of the patients with SID, AIS, allergic diseases and LAP increased 1.27-fold (p < 0.02), 1.31-fold (p < 0.1), 1.31-fold (p < 0.001) and 1.27-fold (p < 0.05), respectively. Under the same conditions production of IFN-gamma by leukocytes of the patients with SID, AIS, allergic diseases, LAP and BAS increased 1.69-fold (p < 0.001), 2.42-fold (p < 0.01), 1.63-fold (p < 0.001), 1.4-fold (p < 0.1) and 1.69-fold (p < 0.05), respectively. The data obtained may be useful for understanding mechanisms of the IFN system deficiency development in immunopathological disorders, as well as for further development and improvement of IFN therapy.