Intracardial electrophysiological examination was conducted in 50 patients with suspicious or confirmed data about disturbed function of sinus node--namely: short-term auricular stimulation for determination of sinoatrial time (SAT) and long-term auricular stimulation with increasing frequency with analysis of the phenomena in the post-stimulation period--time of sinus node recovery (TSNR), corrected recovery time of sinus node (CRTSN=TSNR minus the basal cycle of auricle before stimulation), emerging of ectopic rhythm leaders and secondary pauses. The following data were obtained in the two groups of patients formed: Group I--26 patients with ECG data about disturbed function of sinus node (periods of sinus bradycardia under 40 beats (minute and/or sinus pauses over 1800 msec): SAT identical to 375 +/- 168; TSNR = 2714 +/- 562; CRTSN = 1684 +/- 347; SAT over 400 msec was found in 8 out of 22 patients; TSNR over 1400 msec in 20 out of 26 patients, CRTSN over 550 msec in 20 out of 26 patients. Ectopic rhythm leader occurred in the poststimulation interval in 5 out of 26 patients and in 4 patients--secondary pauses over 1800 msec were observed; Group II--24 patients, with no data about disturbed function of sinus node (according to the upper criteria): SAT = 254 +/- 91; TSNR +/- 1082 +/- 168; CRTSN = 326 +/- 108; SAT over 400 msec was observed in none of the patients from that group. TSNR over 1400 msec (but under 1700 msec) was found in one patient, CRTSN in the same patient and in the rest of that group was under 550 msec. No ectopic rhythm leaders and secondary pauses over 1200 msec were found in that group of patients during the poststimulation interval. SAT, TSNR and CRTSN were shortened with a statistical significance in both the patient groups after the administration of atropine--I mg intravenously and the reexamination but in 5 patients from group I TSNR, CRTSN were paradoxically lengthened and became pathological. The electrophysiological methods for the studies on sinus node and the electrophysiological parameters, obtained via them, could contribute to the characterization and assessment of the functional potentialities of sinus node as well as to a better understanding of the mechanism of its injury.