In order to assess the effects of testosterone undecanoate (TU; 120 mg/d orally for 2 months) on serum lipid, lipoprotein, and apolipoprotein levels in healthy elderly men, the placebo (PL) controlled study was performed on 37 elderly men, aged between 53 and 89 years. In all subjects venous blood samples were taken after an overnight (10 hours) fast and sera were stored -70 degrees C until analysis. In PL group, neither hormonal data nor lipid, lipoprotein, and apolipoprotein levels showed significant changes. After TU supplementation, serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and estradiol (E2) levels decreased from 198 +/- 30.7 mg/dl to 174 +/- 41.9 mg/dl (p < 0.05), from 111 +/- 18.14 mg/dl to 87.9 +/- 29.4 mg/dl (p < 0.01), and from 86.2 +/- 16.9 pmol/l to 70.5 +/- 18 pmol/l (p < 0.01), respectively. Statistically significant differences were not observed in the serum triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and apolipoprotein (apo) A-1 and apo B levels after TU treatment. The mean ratios TC/HDL-C and LDL-C/HDL-C as coronary risk factor criteria decreased significantly in the TU but not in the PL group. No obvious side effect was observed in those who took TU except for reported pyrosis in 2 of 17 elderly men. These data indicate that the increased serum levels of total testosterone (TT) produced by administration of TU, 120 mg/d orally for 2 months lead to suppressed levels of TC and LDL-C and E2 but not significantly changed levels of TC, HDL-C, apo A-1 and apo B. Thus, we conclude that TU may be an effective drug for protecting coronary heart disease in healthy elderly men with lowered TT and FT levels. It may also have beneficial effects for sexual function and behavior.