Obstructive sleep apnea (OSA) is often accompanied by cardiovascular and metabolic disorders. The renin-angiotensin system plays an important role of the cardiovascular regulation. The activity of the angiotensin converting enzyme is genetically determined. The aim of the study was to estimate the relation between angiotensin converting gene polymorphism and cardiovascular diseases or familial history in patients with obstructive sleep apnea. 63 patients with OSA were enrolled to the study. Arterial hypertension was diagnosed in 30 cases, ischaemic heart disease in 5 cases and 10 patients suffered from both mentioned diseases.The observed ACE genotype frequencies in the study group were II: ID: DD: 23.81: 47.62: 28.57%, in the hypertension subgroup II: ID: DD--30.0: 46.6: 23.3%. No differences in the study group were observed in relation to familial history :DI:II--30.43: 43.48: 26.09% vs 25.64: 48.72: 25.4%.1. In the study group there was no association between ACE polymorphism and OSA. 2. There were also no association between the polymorphism of ACE and cardiac diseases or familial history of cardiac diseases in OSA group. 3. The polymorphism of ACE is not a risk factor for OSA.