Background/Aim: The estrogenic actions of tamoxifen on lipid profiles and hemostasis have been extensively demonstrated in women. Due to limited experience with this drug in males, it is uncertain whether these effects are also present in men. The aim of our study was to assess the response of blood lipids, lipoproteins, and coagulation parameters in a group of men taking tamoxifen. Methods: We studied 15 healthy boys with pubertal gynecomastia who were given 10 mg tamoxifen per day. Total testosterone, sex-hormone-binding globulin, estradiol, serum lipids, apolipoprotein B, apolipoprotein A-I, lipoprotein(a), fibrinogen, antithrombin III, von Willebrand factor, and markers of activated coagulation and fibrinolysis were determined at baseline and 1 and 3 months after beginning of the tamoxifen treatment. Results: Total cholesterol and lipoprotein(a) showed moderate but significant decreases from baseline. Low-density lipoprotein and high-density lipoprotein cholesterol concentrations as well as triglyceride and apolipoprotein B levels became lower, but these changes were not statistically significant. Among clotting parameters, antithrombin III was reduced, and von Willebrand factor increased significantly. Markers of activated coagulation and fibrinolysis remained unchanged throughout the period of therapy. Conclusions: The effects of tamoxifen on blood lipids and hemostasis we found in this group of healthy young men were qualitatively similar, but lesser than those previously described in women.