Aim: Male-to-female (MTF) transsexuals are treated with estrogen with and without progestin through a variety of routes. The aim of this study is to evaluate the arterial stiffness in MTF transsexuals undergoing hormonal treatment. Methods: We evaluated the arterial stiffness in 156 MTF transsexuals (22 untreated and 129 treated with estrogen only or plus progestin) using a volume-plethysmographic apparatus equipped with a multi-element applanation tonometry sensor. Results: MTF transsexuals treated with parenteral estrogen were significantly older than untreated MTF transsexuals. Hematocrit, uric acid and activated partial thromboplastin time in treated MTF transsexuals were significantly lower than in untreated MTF transsexuals. The level of high-density lipoprotein cholesterol in MTF transsexuals treated with oral estrogen was significantly higher than in untreated MTF transsexuals or those treated with parenteral estrogen with and without progestin. The systolic blood pressure in MTF transsexuals treated with estrogen only is significantly lower than that in untreated MTF transsexuals. The brachialankle pulse wave velocity was significantly decreased in MTF transsexuals treated with estrogen compared to that in untreated MTF transsexuals or in those treated with estrogen plus progestin. The carotid augmentation index in MTF transsexuals treated with oral estrogen was significantly lower than that in MTF transsexuals treated with parenteral estrogen or oral estrogen plus progestin. Conclusions: Estrogen treatment is likely to have some beneficial effects on lipid metabolism and vascular function in MTF transsexuals; however, progestin administered with estrogen may have adverse effects on arterial stiffness.