Publisher Summary This chapter discusses the structure and function of the epididymis, including the formation of a luminal fluid microenvironment, sperm maturation, and sperm transport. It discusses specifically on the manner, by which the epididymis protects the maturing spermatozoa. Spermatozoa leave the testis neither fully motile nor able to recognize or fertilize an egg, but must traverse a long duct, the epididymis, to acquire these abilities. These transformations of the spermatozoa are collectively referred to as sperm maturation. Even though sperm have developed the ability for motility and to fertilize, they still need to undergo a further maturation step in the female reproductive tract before they achieve their full fertilization potential. In addition, to the numerous changes that the maturing spermatozoa are undergoing during their transit along the epididymal duct, the epididymis also protect spermatozoa from the external environment. The epididymis is an androgen-dependent organ, where many aspects of the epididyma1 function, including the processes of sperm maturation and storage require the presence of androgens.