Atrial fibrillation (AF) remains a frequent complication of cardiac surgery. The optimal treatment strategy has not been established. Retrospective studies have suggested that a primary rate-control strategy may be equivalent to a strategy that restores sinus rhythm. Fifty patients with postoperative atrial fibrillation were randomly assigned to a strategy of antiarrhythmic therapy +/- electrical cardioversion or ventricular rate control. Anticoagulation with heparin overlapped with coumadin was administered to both arms. The primary endpoint of the study was time to conversion to sinus rhythm analyzed by the Kaplan-Meier method. The effects of strategy on hospital length of stay was examined as well as the incidence of recurrent AF. This study demonstrated no significant difference between an antiarrhythmic conversion strategy (n = 27) and a rate-control strategy (n = 23) in time to conversion to sinus rhythm (11.2 +/- 3.2 vs. 11.8 +/- 3.9 hours; p = 0.8). With Cox multivariate analysis to control for the effects of age, sex, beta-blocker usage, and type of surgery, the conversion strategy showed a trend toward reducing the time from treatment to restoration of sinus rhythm (p = 0.08). The length of hospital stay was reduced in the antiarrhythmic arm compared with the rate-control strategy (9.0 +/- 0.7 vs. 13.2 +/- 2.0 days; p = 0.05). In hospital relapse rates in the antiarrhythmic arm were 30% compared with 57% in the rate-control strategy (p = 0.24). At the termination of the study, 91% of the patients in the rate-control arm were in sinus rhythm compared with 96% in the antiarrhythmic arm. In conclusion, this pilot study shows little difference between a rate-control strategy and a strategy to restore/maintain sinus rhythm. Regardless of the strategy, majority of patients will be in sinus rhythm after two months. A larger randomized, controlled study is needed to assess the impact of restoration of sinus rhythm on length of stay.