Background and Purpose— The influence of age on the relationship between obstructive sleep apnea (OSA) and the incidence of hard cardiovascular events remains controversial. We sought to analyze the relationship between OSA and the incidence of stroke and coronary heart disease in a large cohort of elderly patients, as well as to investigate the role of continuous positive airway pressure (CPAP) treatment in these associations. Methods— Post hoc analysis of a prospective observational study of consecutive patients ≥65 years studied for OSA suspicion at 2 Spanish University Hospitals. Patients with an apnea-hypopnea index (AHI) <15 were the reference group. OSA was defined by an AHI ≥15 and classified as untreated (CPAP not prescribed or compliance <4 hours/day), mild-moderate (AHI 15–29), untreated severe (AHI ≥30), and CPAP-treated (AHI ≥15 and CPAP compliance ≥4 hours/day). Results— 859 and 794 elderly patients were included in the stroke and coronary heart disease analyses, respectively. The median (interquartile range) follow-up was 72 (50–88.5) and 71 (51.5–89) months, respectively. Compared with the reference group, the fully adjusted hazard ratios for the incidence of stroke were 3.42 (95% CI, 1.37–8.52), 1.02 (95% CI, 0.41–2.56), and 1.76 (95% CI, 0.62–4.97) for the untreated severe OSA group, CPAP-treated group, and untreated mild-moderate OSA group, respectively. No associations were shown between any of the different OSA groups and coronary heart disease incidence. Conclusions— The incidence of stroke, but not coronary heart disease, is increased in elderly patients with untreated severe OSA. Adequate CPAP treatment may reduce this risk.