Intracavernous pharmacotherapy of erectile dysfunction has been established for over 10 years, with prostaglandin E1 (PGE1) being the standard substance with the lowest rate of side effects. Recent investigations deal with the identification of intracellular mechanisms of smooth muscle relaxation in cavernous tissue as the most important aspect of penile erection. Nitric oxide and specific phosphodiesterase-isoenzymes seem to play a central role. This resulted in clinical studies with the intracavernous injected nitric oxide-donor linsidomine (SIN 1) and the orally given phosphodiesterase-inhibitor sildenafil. Furthermore new ways of pharmaco-application are tested, e.g. transdermal treatment with nitroglycerin, minoxidil or papaverine, as well as intraurethral injection of prostaglandin E1.