The long-term efficacy of testosterone supplementation for erectile dysfunction was evaluated using standardized questionnaires and differences between testosterone delivery systems analyzed. Forty-four patients receiving parenteral depo-testosterone, Testoderm scrotal patches, or Testoderm-TTS nonscrotal patches were evaluated with the Erectile Dysfunction Inventory of Treatment Satisfaction and International Index of Erectile Function questionnaires. Global questions regarding libido, energy, and improved erections demonstrated a significantly better response with depo-testosterone and Testoderm-TTS nonscrotal patches as compared to Testoderm scrotal patches. Testoderm-TTS nonscrotal patches and depo-testosterone resulted in significantly higher overall treatment satisfaction (p <.001), confidence in ability to engage in sexual activity (p <.001), and total Erectile Dysfunction Inventory of Treatment Satisfaction and International Index of Erectile Function scores (p <.001). Testoderm-TTS nonscrotal patches were significantly better than depo-testosterone with regard to satisfaction with sexual intercourse (International Index of Erectile Function question 5, p <.05). Testosterone replacement improved the quality of erections and level of libido in patients with erectile dysfunction. Treatment delivery systems appear to impact the success of therapy.