Transdermal testosterone patches and topically applied gels have become well accepted for the treatment of testosterone deficiency in men and are currently being developed in appropriate dosage strengths for androgen therapy in women. The furthest developed among these products is an investigational testosterone matrix patch which is now in phase III clinical trials for the treatment of sexual dysfunction in oophorectomized and naturally menopausal women. This review article discusses the biopharmaceutical rationale for the transdermal delivery of testosterone to women, illustrates and quantitatively analyzes the pharmacokinetics and metabolism of the testosterone matrix patch and a recently investigated testosterone gel, and summarizes the efficacy and safety data that have been reported in phase II studies of the testosterone matrix patch in surgically menopausal women with sexual dysfunction and HIV-infected women with the AIDS wasting syndrome. The different effects of oral and transdermal estrogen therapy (ET) on the concentrations of total and free testosterone attained with the testosterone matrix patch are contrasted. Although still in development, transdermal testosterone therapy appears to be a promising new approach for providing physiologically based androgen therapy to women.