The kidneys in two viviparous species of Neotropical lizards, Notomabuya frenata and Aspronema dorsivittatum (Mabuyidae), were investigated by light and scanning electron microscopy in order to determine the presence of the sexual segment of the kidney (SSK) and to study its morphology. The individuals used in this study belong to the Herpetological Collection of the Herpetology Laboratory - Reptiles of the Federal University of Juiz de Fora (CHUFJF-Reptiles) and they were collected between the years 2008 and 2012 from the Cerrado region in the state of Minas Gerais, Brazil. The SSK was present only in sexually mature males (with sperm in the testes / epididymis), whereas it was absent in sexually immature males. The nephron in both species consists of renal corpuscle, proximal convoluted tubule, distal convoluted tubule, collecting duct and sexual segment of the kidney. The SSK of the analyzed species were coated with a simple columnar epithelium, with high cells, basal nucleus and in the apical portion innumerable secretory granules. This study adds to the knowledge on reproductive biology and structures related to reproductive strategies of both lizard species and viviparous Neotropical lizards.