This paper presents a synthesis of a comparative leaf anatomy (lamina and petiole) of five species of the genus Terminalia found in southwest Nigeria. Collections of plants were made from different locations in Southwest Nigeria as the geographic locations of the sites of collection were also georeferenced with a GPS device. The samples were identified at the Herbarium of Botany Department, Obafemi Awolowo University (Ife), Nigeria, and were subjected to anatomical examinations. Quantitative data were subjected to statistical analysis and the characters vary significantly (P = 0.05). Anatomical characters which separate the taxa include petiole outline, epidermal features, vascular pattern, occurence of cortical and pericyclic fibres, presence/absence of, and types of trichomes etc, all found to be useful in identification of different species. The variations in the anatomical traits could be effectively used in taxonomic delimitation of the species and are helpful characters in determining the complexes in the genus such as adaptation of the species to xeric environments. The presence of 2-3 layers of palisade mesophyll cells in Terminalia mantaly, which is an adaptation of the species to drought, is diagnostic for the species. It is suggested that a comprehensive consideration of leaf lamina and petiole anatomy should be used as basis of taxonomy.