Disorders of the genesis and conduction of impulses in different parts of the cardiac conduction system are the result of functional or morphological damage of parts of the conduction system. Pathological processes which affect the cardiac conduction system are practically always comprehensive and ensue from the character of the basic disease. Previous embryological and histological investigations provide evidence of developmental and structural similarity of all portions of the cardiac conduction system. On this fact the assumption of a similar reaction of the conduction system to the acting pathological process is based. In a group of 127 patients with a positive finding, on invasive examination of the conduction system in 57 (45%) a pathological process was detected at several levels of the conduction system. This finding is consistent with experience reported in the literature and supports the justification of the term "disease of the cardiac conduction system" when there is evidence of multi-focal damage of the conduction system.