Although the Ephemeroptera have been studied over a long period of time, there are still few studies on the morphology of male reproductive system. The spermatic ducts are considered conserved among different Ephemeroptera groups. However, previous studies distinguished different organizational patterns of the spermatic duct intrinsic musculature. This study describes the morphology of the spermatic ducts, especially their musculature, in six species of Ephemeroptera, representing five families. We have observed variations in the organizational pattern of the spermatic ducts, even between species from the same family. Moreover, all species studied had intrinsic musculature in the spermatic ducts although with different organizational patterns. Thus, we believe that this musculature is important to move the spermatozoa along the ducts of all Ephemeroptera and not only of those with aflagellated spermatozoa (Leptophlebiidae). The variations in musculature organization must be related to differences in reproductive physiology (i.e., copula duration) and not only with spermatozoa characteristics.