Experience with intracardiac recording of sinus node electrograms (SNE) in 27 patients is described. Under fluoroscopic monitoring the poles of a tri- or quadripolar catheter were positioned at the superior vena cava--right atrium junction. For recording, high amplification of 100 microV/cm and low-pass filters of 0.2-70 Hz were used. SNE was verified by simultaneously recording electrograms from two pairs of poles at the same filter setting and the application of carotid sinus massage. SNE was obtained in 17 patients (63%). It was recognized as a smooth, low-frequency upstroke slope before rapid atrial depolarization. Its amplitude range was 30-90 microV. Directly recorded sinoatrial conduction time (SACT) ranged from 55 to 120 ms (mean 88 +/- 20). In 4 patients with sick sinus syndrome SACT varied from 90 to 220 ms. SACTs calculated by the premature stimulation method and measured directly from SNE were in good correlation (r = 0.61, p less than 0.05).