The incidence and diagnostic criteria of heart rhythm disorders associated with a permanent pacemaker were assessed on the basis of data, obtained at a single electrocardiography in 1165 patients and continuous ECG recording in 49 patients. A high (94.4%) incidence of the spontaneous and induced rhythm competition at asynchronous stimulation has been demonstrated, indicating that the use of this stimulation regimen should be abandoned. The inhibition of a unipolar pacemaker by myopotentials at regular physical activity is rather uncommon and has no clinical value. VVI stimulation is often (45.2%) associated with variants of escape-capture bigeminy.