Erectile dysfunction is a common sequela following potentiallycurative local treatment for early-stage carcinoma of the prostategland. With larger studies and longer follow-up, it is clear that erectiledysfunction following prostate brachytherapy is more common thanpreviously reported, with a myriad of previously unrecognized sexualsymptoms. Approximately 50% of patients develop erectile dysfunctionwithin 5 years of implantation. Several factors including preimplantpotency, patient age, the use of supplemental external-beam irradiation,radiation dose to the prostate gland, radiation dose to the bulb ofthe penis, and diabetes mellitus appear to exacerbate brachytherapyrelatederectile dysfunction. The majority of patients with brachytherapy-induced erectile dysfunction respond favorably to sildenafil citrate(Viagra). Despite reports questioning the potency-sparing advantageassociated with brachytherapy, recent elucidations of brachytherapyrelatederectile dysfunction may result in refinement of treatmenttechniques, an increased likelihood of potency preservation, andultimately, improved quality of life.