Many patients report problems of impotence after heart transplantation, which definitely impairs their quality of life. Ten men, with a mean age of 41 years, were evaluated for persistent erection problems after heart transplantation by measurement of nocturnal penile tumescence using a Rigiscan. Three men had a positive response, and their disturbances were therefore considered to have a psychological basis; seven men had a negative or only weakly positive response, and their impotence was attributed to organic causes. To all patients, intracavernous injections of an initial dose of 10 to 20 micrograms of prostaglandin E1 were administered as first-choice treatment. Nine patients obtained a firm, lasting erection 2 to 5 minutes after injection, with no relevant side effects. The patients were then instructed to self-administer the drug before intercourse, and some were able to return to spontaneous sexual activity at various intervals. Intracavernous injection of prostaglandin E1 seems to be an effective treatment of erectile impotence in heart transplant recipients; it is well tolerated with no side effects and considerably improves the patient's quality of life.