Despite recent advances in its treatment, congestive heart failure associated with depressed left ventricular function continues to be associated with excess morbidity and mortality. Multiple factors may contribute to the progressively declining course of heart failure. Nocturnal arterial oxyhemoglobin desaturation caused by sleep-disordered breathing could be a contributing factor, particularly because it has been associated with excess mortality in patients with chronic obstructive pulmonary disease. Cheyne and Stokes were the first to observe periodic breathing in patients with heart failure (Cheyne-Stokes respiration). However, relatively large-scale systematic studies have been performed only recently. We studied 42 patients with stable, optimally treated heart failure, without other co-morbid disorders: 19 patients (45%) had an apnea-hypopnea index of more than 20/hour. These episodes were associated with an excess number of arousals and arterial oxyhemoglobin desaturation. Treatment options include nocturnal administration of oxygen, continuous positive airway pressure (CPAP), and medications such as theophylline. Large-scale studies are needed to evaluate the efficacy of these treatment options on quality of life, morbidity, and mortality of patients with heart failure.