Thirty percent of males af¯icted with erectile dysfunction (ED) do not respond to oral drugs, another 15% reveal contraindications to currently available therapy, and a subset of patients actually prefer injection therapy due to its predictable short time-to-onset of erection and reliable rigidity compared to oral drugs. This paper provides both a historical and current perspective on intracavernosal therapy and reviews the popular injectable therapeutic agents that are currently used for the treatment of ED. Emphasis is placed on the ef®cacy, mechanism of action and side effect pro®les of approved and experimental injectable pharmacotherapy for ED.