AIM: To investigate the effects of testosterone on endothelial function and intimal proliferation after balloon injury in male rabbit abdominal aorta. METHODS: 24 male New Zealand white rabbits were divided randomly into three groups: control group ( n =8, sham castration), hypotestosteronemia group ( n =8,castration) and testosterone replacement group (n =8,castration +testosterone undecanoate intramuscular injection,14 mg/kg). Abdominal aorta was injured with 3 mm PTCA balloon after testosterone undecanoate had been injected for three days. Two weeks later, blood samples were obtained for detection of plasma testosterone, lipids, metabolic product of nitric oxide (NO - 2/NO - 3), superoxide dismutase(SOD) and malondialdehyde (MDA),and all the abdominal aorta were excised to be analyzed by computer. RESULTS: The intimal area of hypotestosteronemia group were significantly larger than that of other two groups( P