Cardiac glycosides are used as positive inotropic agents in the treatment of heart rhythm disorders. Digitalis species have been used as a source of these components for many years. Digitalis trojana Ivanina is an endemic plant of Ida Mountain (KazdagÄ±), Çanakkale, Turkey. In this study, we report the cardenolide content changes of Digitalis trojana Ivanina which was collected from KazdagÄ± at different altitudes (836m, 961m, 1041m and 1191 m). The content of lanatoside C, digoxin, digitoxin and gitoxigenin in the plant samples were analysed by HPLC. According to the results of analyses, cardenolide contents of D. trojana (lanatoside C, digoxin, digitoxin and gitoxigenin) showed variations by altitude (836m, 961m, 1041m and 1191 m) and month (May and July). It was determined that these cardenolides were higher in plants collected in July than in May and the highest cardenolide concentration was found in the samples collected at 1047 m. both in May and July.