To date, there are multiple studies detailing the ultrastructure of spermatozoa within the genus Aspidocelis and within the family Teiidae. However, there are no complete data on the process of spermiogenesis within a species of Whiptail Lizard or within Ground Lizards. The purpose of this investigation is to provide the first detailed study on the entire ultrastructural process of spermiogenesis within Aspidocelis costata. These results can then be compared to the spermatozoa data that is available for Teiidae. Testicular tissues of A. costata were fixed,dehydrated, embedded in epon812, sectioned with an ultramicrotome, and viewed using transmission electron microscopy (TEM). Lizard spermatid morphology in recent studies have been found to be relatively conserved to one another within Squamata. Unlike spermatozoa,however, small differences during the development of the spermatids within lizards of the same genus have been observed with Transmission Electron Microscopy (TEM). Thus, we hypothesize from the preliminary data collected to date that differences in acrosome formation, midpiece morphology, nuclear morphology, and manchette morphology will be observed between the spermatids of A. costata and others within Teiidae. We hope that the data provided here will add to the growing information about spermatid development in lizards. These data will provide new species and familial characteristics that can be compared to that of the previously studied saurian taxa.