The human penile venous system has been well studied and described but the demonstration of extra venous channels in imaging films prompted us to seek refinement of our anatomical knowledge of this venous system. Cavernosography in 37 patients who had venous stripping surgery and now suffered recurrent erectile dysfunction consistently showed an independent vein, smaller than the deep dorsal vein, running almost in the same position of the deep dorsal vein even though the latter had been removed unequivocally in previous surgery. Cavernosography in 9 patients who underwent intraoperative films also demonstrated the presence of this cavernosal vein in addition to the deep dorsal vein. Meticulous dissection of the penis under the microscope was then performed in 21 male cadavers and we found a cavernosal vein coursing along each corpus cavernosum all the way distally to the glans and draining directly into the Santorini's plexus in 19 subjects. This is in contrast to the previous description that this cavernosal vein was a short vein in the penile hilum. Two sets of para-arterial veins, which have not been reported in the literature, were found to accompany each dorsal artery in all 21 subjects. This more extensive and extra venous drainage might have important implication for venous stripping surgery in the treatment of erectile dysfunction.