This study reports polysomnographic features of five patients with Cheyne-Stokes respiration (CSR). They were referred for evaluation of presumptive sleep apnea syndrome on the basis of history and physical examination, but were found to have predominantly CSR on all-night sleep study. On the initial polysomnographic study, CSR comprised 47 to 86% of all disordered-breathing events. Cheyne-Stokes respiration resulted in considerable oxyhemoglobin desaturation (mean baseline saturation was 95 +/- 4 +/- SD, and lowest saturation was 76 +/- 8). More than one-half of all CSR events resulted in awakenings or arousals. Evidence of upper airway obstruction was noted in the majority of CSR events in three of five patients. Four patients were treated with theophylline; one who refused drug therapy was treated with nasal continuous positive airway pressure (CPAP). Comparison of sleep studies before and after therapy showed a significant decrease in the CSR index (29 +/- 11 versus 2 +/- 2) and in the maximal oxyhemoglobin desaturation associated with CSR (13 +/- 5 versus 3 +/- 2), and an improvement in lowest O2 saturation associated with CSR (76 +/- 8 versus 91 +/- 4). Total disruptions in sleep architecture per hour of sleep improved significantly with therapy (46 +/- 21 versus 20 +/- 8). We conclude that the clinical presentation of CSR can be indistinguishable from that of the "traditional" sleep apnea hypopnea syndrome and can result in major oxyhemoglobin desaturation and sleep fragmentation. Theophylline results in considerable improvement in the disordered breathing of CSR during sleep.