There have been few studies examining the relationship between NOD and mortality in patients with COPD and none examining this relationship in those patients with a daytime PaO2 greater than 60 mm Hg. Is NOD related to early death, and if so, should nocturnal supplemental oxygen be considered as therapy for altering survival? We examined survival in 169 COPD subjects. Two definitions were used to classify subjects as NOD and non-NOD, one considering episodic desaturation associated mainly with REM sleep (definition 1) and one considering greater than 30 percent of time in bed spent below an SaO2 of 90 percent (definition 2) to be significant. Survival corrected for age was significantly better in non-NOD subjects. However, when stratified for supplemental oxygen use, survival remained better only in subjects separated by definition 1. There was a trend toward increased survival in 35 oxygen-treated vs 38 non-oxygen-treated NOD subjects (definition 1), but this difference was not statistically significant.