The objective of this study was to describe some changes in spermatids differentiating events during spermiogenesis, leading to spermatozoa final formation. The animals were sacrificed with ethylic acid inhalation and, then, testis fragments were collected, fixed in Karnovsky and post-fixed in osmium tetroxide. After dehydration, the sections were stained with uranyl acetate 2%. It was observed in early spermatids at Golgi phase, formation of acrosomal granule contained in the acrosomal vesicle, spheroidal nucleus with rugous reticulum around it, and Golgi apparatus made up of lamellae and vesicular structures. At cephalic hood phase, the granule suffers flattening and the marginal fossa is formed. In both phases, it was possible to observe the presence of multivesicular body. At acrosomal phase, the acrosomal system is set up, and several enzymes of endoplasmatic reticulum as well chromatoid body are observed in the cytoplasm. At the last phase, that is, maturation, the nucleus becomes more elongated, the endoplasmatic reticulum regresses, the Golgi apparatus approaches to the flagellum and mitochondrias align next to it