A study was made of the immune system of patients with chronic HB-viral infection who showed the signs of secondary immundeficiency. The high frequency of the impairment of immunocompetent cells seen in chronic hepatitis B was established as was the appearance of different-temperature autolymphocytotoxins in response to the infection of mono-nuclears in all the disease stages. The treatment with thymalin proved effective in patients with the lack of cold autolymphocytotoxins or in those with low activity of the latter ones. The combined treatment (decaris plus prednisolone) turned out effective in children with a pronounced autoimmune component of the process (the presence of cold autolymphocytotoxins). It has been shown that the discovered interrelations between the different components of the immune system are conductive to the determination of the pathological process type and the choice of adequate therapy.