Sleep-induced periodic breathing has been suggested to lead to the development of occlusive apneas in patients with sleep apnea syndrome. If this were true, patients with Cheyne-Stokes respiration should also develop upper airway occlusion during sleep. To study this hypothesis, 6 nonobese patients with Cheyne-Stokes respiration lacking evidence for sleep apnea syndrome and anatomic upper airway abnormalities underwent polysomnography during daytime naps. A total of 463 apneas were analyzed in the 6 patients studied. In 1 patient, no evidence of upper airway occlusion was observed. In the remaining 5 patients, a varying frequency of upper airway occlusion resembling the pattern of mixed apnea was seen in 3 to 97% of the total apneas analyzed. The mean number (+/- 1 SD) of occluded inspiratory efforts per mixed apnea in these 5 patients was 1.69 +/- 0.59. These results show that patients with Cheyne-Stokes respiration may develop upper airway occlusion during sleep and are consistent with the contention that sleep-induced periodic breathing in patients with sleep apnea syndrome is primary to the development of occlusive apneas.