Since 1987, the authors have observed the therapeutic effect of Xin Bao on 87 patients with sick sinus syndrome. Electrophysiological stimulation examination: SNRT greater than 1900 ms and CSNRT greater than 600 ms in all patients. Routine ECG and Holter monitoring ECG: (1) Persistent sinus bradycardia or/and atrio-ventricular junction escape rhythms or/and premature beat, heart rate less than 48 +/- 6 beats/min in 40 patients; (2) sinus standstill (arrest) or secondary degree sinoatrial block in 10 patients; (3) bradycardia-tachycardia syndrome in 30 patients; (4) the heart rate greater than 60 beats/min in 7 patients. The major symptoms were dizziness, palpitation, chest press, malaise, remission in memory, nocturia, amaurosis and Adams-Stokes syndrome, etc. Self-comparison was taken, Xin Bao was given 2-10 tablets 2 or 3 times a day by oral administration for 2 months. The major symptoms of sick sinus syndrome was greatly improved after treatment. The total effective rate attaining to 85%. The improvement in heart function was also significant, the total effective rate being 80%. After treatment SNRT and CSNRT were shortened (P less than 0.01), the total heart beats for 24 hours and the average heart beats/min greatly increased (P less than 0.01). CO and EF increased too (P less than 0.05). No serious adverse reactions were found during the treatment. It was believed that Xin Bao could stimulate sino-atrial node and increase it's excitability. The basic heart rate was increased and the heart function improved with no adverse reactions. It may be administrated in long term. Therefore, Xin Bao may be recommended as appropriate drug for treating sick sinus syndrome.