For two consecutive nights, 20 patients with chronic obstructive pulmonary disease (COPD) without significant carbon dioxide retention were monitored by polysomnography in a sleep laboratory study of the effects of flurazepam ingestion. In a double-blind, controlled, randomized fashion, they ingested 30 mg of flurazepam or placebo on one night and the alternate compound on the other night. Flurazepam increased the frequency of sleep-disordered breathing events (p less than 0.01), the frequency of episodes of desaturation (p less than 0.01), the duration of desaturation (p less than 0.01), and the severity of desaturation (p less than 0.05). Although the findings were significant, the magnitude of the changes was small. In 17 of the 20 patients, the ingestion of a single 30-mg flurazepam tablet did not cause clinically significant oxygen desaturation or breathing disturbance. The active drug did increase total sleep time (p less than 0.001) and thus was an effective hypnotic in patients with COPD.