Clinico-anatomical analysis of 112 lethal cases of diphtheria in adults showed a grave course of the disease in chronic alcoholics at the age of 40-49 years. The morphological changes were characterized by a complex of typical changes at the primary focus, intracanalicular and hematogenous dissemination with high bacteremia. The morphology of pneumonia caused by Corynebacterium diphtheria is described for the first time. At the early stages of the disease infectious-toxic degeneration of the myocardium was documented with predominating alteration of the atrioventricular node or contractile myocardium. The above morphological features may be due to peculiarities of patients and decreased subjects as well as possible changes in the pathogen characteristics.