Dihydroandrostenedione (Androstanedione) is a steroid metabolite and a precursor of both testosterone and estrone normally produced by the adrenal gland and gonads and is converted to testosterone through the action of 17β-hydroxysteroid dehydrogenase, which is found in most body tissues. Androstenedione is also produced by some plants and has recently been marketed as a product for increasing blood testosterone concentrations to be used as a natural alternative to anabolic steroid use. However, androstenedione administration during resistance training did not significantly alter the serum testosterone concentration in normotestosterogenic young men. The increased muscle size and strength observed with resistance training were also not augmented with androstenedione administration. The use of androstenedione increased the serum concentrations of estradiol and estrone, suggesting an increased aromatization of the ingested androstenedione and/or testosterone derived from the exogenous androstenedione. The use of androstenedione was associated with decreased levels of HDL-C. These data provide evidence that androstenedione does not enhance adaptations to resistance training and may result in potentially serious adverse health consequences in young men.