Oxidative damage may occur during hypoxia. Under hypoxic conditions, elderly have weaker defense against oxidative damage. The present study aims to examine the effects of acute mild-strength hypobaric hypoxia on aged rats’ myocardial left ventricle oxidative damage. In the study, 24 months’ old Wistar albino rats were used. Following six hours of exposure to 6000 m altitude, heart muscles’ radical damage indicators, i.e. lipid hydroperoxides, protein carbonyl, advanced oxidation protein products, total thiol and protein thiol levels were measured. Both protein carbonyl and lipid hydroperoxide levels in old rats’ heart muscle left ventricles were found to be significantly higher (p