Withdrawal of beta-blocker treatment due to circumstances connected with general and vascular operations was the cause of rapid atrial fibrillation in 5 of 6 patients in whom this complication occurred within one year. Three illustra tive cases are described. The arrhythmia was resistant to digoxin and verapamil and was controlled only after beta-blocker treatment was resumed. The mech anism of this phenomenon is discussed and a regimen for prophylaxis and treat ment is suggested. Increased awareness of this syndrome by general surgeons should reduce the incidence of this complication.