The cyclical and seasonal modifications of the various epididymis regions (ductuli efferentes, head, body and tail) of Chiroptera (Vesperugo savi and Vesperugo piccolo) have been investigated. The ultrastructural seasonal features noticed in the ductus epididymis and principal, clear cells content confirm a double function (absorbing and synthetic) in these cells. Beside it, they seem to underline a close relationship with the phases of spermatogenesis and the eventually significant contributions of the epididymis regions to the spermatozoa maturation.