Perioperative supra ventricular tachyarrhythmias (AF/SVT) have been long recognized as a complication after major surgery, but little is known about the incidence after major nonthoracic surgery. One thousand two hundred ten consecutive patients undergoing total hip or knee arthroplasty were studied to determine the incidence of new onset AF/SVT. Information on preoperative medical history and laboratory tests were collected in a subset of 583 patients, and analyzed using logistic regression and linear analysis to determine risk. Ninety-four-and-one-half percent of patients received an epidural anesthetic, 4.1 % had general anesthesia and 1.3% had spinal anesthesia. New onset AF/SVT was found in 38 of 1210 patients, representing an incidence of 3.1%. In the subset of 583 patients, the incidence was 4.8%. The only variables found to be independently associated with the perioperative development of AF/SVT were a history of atrial fibrillation, increasing age, left anterior hemi-block, and atrial premature depolarizations on the preoperative electrocardiogram. In those patients 60 years of age or older with one or more positive risk factors (13% of the study population), the incidence was 18.2%). In those patients less than 60 years of age with none of the identified risks, the incidence was 1.9%.