Apolipoprotein E (ApoE) is a genetic risk factor influencing the development of cardiovascular diseases and Alzheimer's disease. Patients with obstructive sleep apnea (OSA) suffer an excess mortality and morbidity from cardiovascular diseases. The frequencies of ApoE alleles were determined in 291 patients with OSA and 728 controls. The distribution of ApoE alleles and genotypes showed no difference between OSA and controls.