Intraurethral application of prostaglandin-E1 (MUSE) is a well-tolerated pharmacotherapy for erectile dysfunction. However, the physiological mechanisms of drug transfer into the cavernous bodies are not completely clear. Using spongiosography in 35 patients, our study tried to elucidate existing shunt mechanisms. The X-rays show venous drainage through the deep dorsal vein up to the plexus Santorini. The circumflex veins are also contrasted and the cavernous bodies show opacification in their distal portion only. Structures shunting directly between the corpus spongiosum and the cavernous bodies were not demonstrable. Retrograde filling of the cavernous bodies through the deep dorsal vein and its circumflex braches seems to be the most relevant way of drug transfer after intraurethral application of prostaglandin-E1. Diffusion into the cavernous bodies or a systemic mechanism of action does not seem probable.