To assess the efficacy and safety of a 300 mug/d testosterone patch for the treatment of hypoactive sexual desire disorder in surgically menopausal women on concomitant estrogen therapy. Five hundred thirty-three women with hypoactive sexual desire disorder who had undergone previous hysterectomy and bilateral oophorectomy were enrolled in a 24-week, multicenter, double-blind, placebo-controlled trial. Patients were randomly assigned to receive placebo or the testosterone patch twice weekly. The primary efficacy endpoint was change from baseline at week 24 in the frequency of total satisfying sexual activity, measured by the Sexual Activity Log. Secondary measures included sexual desire using the Profile of Female Sexual Function and personal distress as measured by the Personal Distress Scale. Hormone levels, adverse events, and clinical laboratory measures were reviewed. Total satisfying sexual activity significantly improved in the testosterone patch group compared with placebo after 24 weeks (mean change from baseline, 1.56 compared with 0.73 episodes per 4 weeks, P = .001). Treatment with the testosterone patch also significantly improved sexual desire (mean change, 10.57 compared with 4.29, P < .001) and decreased personal distress (P = .009). Serum free, total, and bioavailable testosterone concentrations increased from baseline. Overall, adverse events were similar in both groups (P > .05). The incidence of androgenic adverse events was higher in the testosterone group; most androgenic adverse events were mild. In surgically menopausal women with hypoactive sexual desire disorder, a 300 mug/d testosterone patch significantly increased satisfying sexual activity and sexual desire, while decreasing personal distress, and was well tolerated through up to 24 weeks of use.