Drug addiction is a current serious medical and social problem. The continuing all over the world during the last several decades tendency of narcotic drug use growth has leaded to significant increase in the number of patients with drug abuse and number of associated internal diseases. A huge number of diseases have the particular features of clinical course in drug addicts with chronic drug intoxication compared to patients without it, which is related primarily to serious disorders of drug addicts’ immune system, i.e. with marked immunodeficiency. Immunotropic drug effects were and still are closely studied, a lot of data concerning various cellular and humoral immunity impairments in patients with substance abuse were gained, but most of them are controversial, scattered and not systemic. Because of immunity reconstitution developing in patients with drug abuse, different infections including viral hepatites, HIV-infection, pneumonias, tuberculosis, infective endocarditis and septicemia are characteristic for this patient subgroup. Further research on etiology, immunopathogenesis and clinical features of those diseases in drug addicts are still actual.