Atrial fibrillation is a growing health problem and the most common cardiac arrhythmia, affecting 5% of persons above the age of 65 years. The number of hospital discharges for atrial fibrillation has more than doubled in the past decade. It occurs very often in patients with congestive heart failure and the prevalence increases with the severity of the disease. These two conditions seem to be linked together, and congestive heart failure may either be the cause or the consequence of atrial fibrillation. The prognosis of atrial fibrillation is controversial, but studies indicate that atrial fibrillation is a risk factor in congestive heart failure patients. In the last 10-15 years, significant advances in the treatment of heart failure have improved survival, whereas effective management of atrial fibrillation in heart failure patients still awaits similar progress. Empirically, two strategies have evolved for treatment of atrial fibrillation: 1) rhythm control, which means conversion to sinus rhythm and maintenance of sinus rhythm; and 2) rate control, which means reduction of heart rate to an acceptable frequency. It is unknown whether one of these strategies is better than the other. In this review the authors discuss the prevalence, impact, and treatment of atrial fibrillation in heart failure patients.