Five patients with congestive heart failure (CHF) and 1 with left ventricular dysfunction but without CHF were found to have sleep apnea. Central sleep apnea (CSA) related to Cheyne-Stokes respiration was seen in 4 cases while obstructive sleep apnea (OSA) was seen in 2. All patients had symptoms of sleep apnea. Nasal continuous positive airway pressure (NCPAP) was effective in reversing CSA and OSA in all patients with improvement in sleep structure and alleviation of symptoms of sleep apnea. In addition, all experienced a reduction in cardiac dyspnea. This was associated with a 5% or greater increase in left ventricular ejection fraction while on NCPAP, compared to baseline value off NCPAP in 5 patients and resolution of chronic pleural effusion and pulmonary edema in the sixth. We conclude that Cheyne-Stokes respiration during sleep may give rise to a CSA syndrome that is reversible by NCPAP. In addition, NCPAP therapy may lead to a reduction in cardiac dyspnea and improvement in left ventricular function in patients with left ventricular dysfunction and sleep apnea.