A total of 72 impotent patients entered into a pharmacological erection program using prostaglandin E1. Of the men 35 (49%) used prostaglandin E1 on a regular basis, while 37 (51%) failed to continue in the program beyond the in-office dose titration period. In patients who continue to use prostaglandin E1 the median duration of drug use is 7 months, with a range of 2 to 28 months. There have been no instances of cavernous fibrosis, systemic reaction or chemical priapism (erection present longer than 4 hours) in any patient. Only 8 men (11%) were unable to achieve an adequate erection with prostaglandin E1 injections. The most common adverse effect of prostaglandin E1 was penile pain after injection. The incidence of severe pain leading to drug discontinuation was 17% (12 of 72 patients) while mild to moderate pain occurred in 22% (16 of 72). Over-all, intracavernous prostaglandin E1 injections appear to be a safe, effective treatment for impotence in most men.