The aim of the study was to investigate genetic characteristics of patients with chronic obstructive bronchitis (COB) using classic biochemical markers, their contribution to the development and course of the disease, and morphological peculiarities of erythrocytes in these patients. The subjects were 60 COB patients and 50 practically healthy people; their serum samples were studied. The following classic biochemical markers were investigated: haptoglobin; transferrin; C3 compliment component; group-specific component; ABO blood systems and Rh-factor. Erythrocytometry of blood smears was performed upon admission and before discharge. The study evaluated the contribution of heredity to the forming of COB and established specific genetic markers of predisposition to the development of COB and certain features of its clinical course; the condition of peripheral blood erythrocytes in COB patients was studied.