beta-Thalassemia major is associated with a high prevalence of hypogonadotropic hypogonadism affecting adolescents and young men with this disease. The pharmacokinetics of Androderm, a non-scrotal permeation-enhanced testosterone transdermal system, was previously studied in this population using three application regimens designed to mimic the nocturnal secretion and circadian patterns of testosterone production characteristics of puberty and young adulthood. In regimen I, designed for prepubertal 14 to 16 year-olds, a single Androderm patch (2.5 mg/day nominal delivery rate) is applied at night and removed 12 hours later in the morning. In regimen II, designed for partially virilized 17 to 19 year-olds, a single Androderm patch is applied nightly for 24 hours. In regimen III, intended for virilized men aged 20 years and older, two Androderm patches (total dose of 5 mg/day) are applied nightly for 24 hours. This report presents the results of a 12-month open label study using these three Androderm regimens to treat nine hypogonadal males with beta-thalassemia (ages 16.8 to 31.8 yr). Our data show that Androderm produced physiologically appropriate testosterone levels, lowered SHBG levels, promoted growth and virilization, increased bone mineral density, and was generally well tolerated in this population of hypogonadal adolescents and young men with beta-thalassemia.