Androgenic-anabolic steroids (AAS) are widely abused by athletes and this abuse has been associated with many serious circulatory events including sudden cardiac death, myocardial infarction and cardiac hypertrophy. The effect of chronic treatment for 16 weeks with testosterone (25mg(-1)kg(-1)week(-1)) and nandrolone (50mg(-1)kg(-1)week(-1)) on serum lipids of male hypercholesterolemic New Zealand rabbits was investigated. The responses of isolated rabbit aortic rings to some vasoconstrictors (epinephrine, serotonin and endothelin-1) and vasodilators (adenosine and sodium nitroprusside) were also measured after treatment. Testosterone and nandrolone significantly reduced HDL-cholesterol levels, potentiated vasoconstriction responses to epinephrine, serotonin and endothelin-1, and attenuated vasorelaxant responses to sodium nitroprusside in rabbits. Nandrolone also caused a significant increase in LDL-cholesterol levels. No significant changes in adenosine relaxation were found in rabbits. The results of the present study showed that the abuse of AAS in presence of hypercholesterolemia can enhance atherogenicity and vasospasm as well as attenuation of vasorelaxation. Therefore the abuse of AAS is harmful to the vascular system and should be prohibited.