the agouti (dasyprocta aguti) is a wild rodent that, in the northeast region of brazil, is a species that is very used by the low-income population as an alternative protein source for human feeding. thirty-one male agouti were used, coming from the universidade federal do piauí (ufpi) - piauí state, and from escola superior de agricultura de mossoró (esam) - rio grande do norte state - brazil. the animals were divided in to age groups, from the birth to fourteen months old. the average diameter average of the nucleus was obtained by measuring 10 nuclei of the studied cellular type, in each testicle that was in the stage i of the seminiferous epithelium cycle. this was performed in animals that did not present an organized epithelium in well-defined periods due to the age, and measurements were made in transversal sections chosen only for the circular contour. the beginning of the asynchronism of the spermatogenic process was observed since the six months of age. the puberty of the agouti dasyprocta aguti was definitely established at nine months of age, because all the cellular types and free spermatozoa in the tubular lumen were present in a large extent of the testicular parenchyma.