Supraventricular tachydysrhythmia is a bothersome and potentially harmful occurrence after coronary artery bypass graft operation (CABG). Use of digoxin prophylaxis preoperatively has yielded conflicting results in lowering the incidence of supraventricular tachydysrhythmia. In this study, three groups of patients were formed. Group 1 served as the control; no prophylactic medication was given. Group 2 was given digoxin prophylaxis beginning immediately after operation. Group 3 received digoxin postoperatively as did Group 2, plus orally administered propranolol beginning on postoperative day 2. No difference in the incidence of supraventricular tachydysrhythmia was found between Groups 1 and 2 (28.2% versus 28.9%). However, the incidence in Group 3 was 2.2%, and this represented a statistically significant difference (p less than 0.005) compared with either Group or 2. The combined use of digoxin and propranolol postoperatively significantly reduced the incidence of supraventricular tachydysrhythmia after CABG.