The evidence linking sleep-disordered breathing to increased mortality and cardiovascular morbidity has been conflicting and inconclusive. We hypothesized that a potential adverse effect of disordered breathing would be more obvious in patients with established vascular disease. In a prospective cohort study 408 patients aged 70 yr or younger with verified coronary disease were followed for a median period of 5.1 yr. An apnea-hypopnea index (AHI) of > or = 10 and an oxygen desaturation index (ODI) of > or = 5 were used as the diagnostic criteria for sleep-disordered breathing. The primary end point was a composite of death, cerebrovascular events, and myocardial infarction. There was a 70% relative increase and a 10.7% absolute increase in the primary composite end point in patients with disordered breathing defined as an ODI of > or = 5 (risk ratio 1.70, 95% confidence interval [CI] 1.15-2.52, p = 0.008). Similarly, patients with an AHI of > or = 10 had a 62% relative increase and a 10.1% absolute increase in the composite endpoint (risk ratio 1.62, 95% CI 1.09-2.41, p = 0.017). An ODI of > or = 5 and an AHI of > or = 10 were both independently associated with cerebrovascular events (hazard ratio 2.62, 95% CI 1.26-5.46, p = 0.01, and hazard ratio 2.98, 95% CI 1.43-6.20, p = 0.004, respectively). We conclude that sleep-disordered breathing in patients with coronary artery disease is associated with a worse long-term prognosis and has an independent association with cerebrovascular events.