In many patients with atrial fibrillation, the most appropriate strategy is 'rate control', designed to slow down the rapid ventricular rates often seen with atrial fibrillation. Based on the hypothesis that symptoms, especially palpitations and exercise intolerance, are due to rapid ventricular rates with activity, optimum rate control usually requires reducing ventricular rates at rest and during activity. Beta-blockers and nondihydropyridine calcium channel blockers are likely more effective than digoxin alone, and the adequacy of rate control is best assessed with heart rate measurement during activity or with ambulatory electrocardiographic monitoring. Taking a patient's symptoms into account, reasonable target ventricular rates are less than 80 beats/min at rest and less than 100 beats/min, on average, over 24 h.