To investigate the effects of a continuous positive airway pressure (CPAP) of 5 cmH₂O for three months on sleep disordered breathing and cardiac function in congestive heart failure (CHF), we performed physiological tests before and after the CPAP treatment in six male patients with stable CHF, whose echocardiographic left ventricular ejection fraction (LVEF) was below 30%. The control polysomnography revealed that all six had Cheyne-Stokes breathing(with central sleep apnea in four, and central sleep hypopnea in two). Prior to the CPAP, the number of episodes of apnea/hypopnea per hour of sleep, the contribution of slow wave sleep to total sleep time, LVEF and the cardio-thoracic ratio were 34.7± 21.4, 4.1± 1.5%, 24.4± 2.3% and 58.4± 3.7% (mean± SD), respectively. After the CPAP, these values changed to 6.0± 7.0, 16.5± 8.3%, 34.3± 3.3% and 55.0± 4.2%, respectively, all of which changes showed a statistical significance (p< 0.05). We conclude that CPAP is an effective treatment for CHF with Cheyne-Stokes breathing, improving sleep disordered breathing, sleep quality and cardiac function, and providing a new non-pharmacological approach for CHF.