M.Sc. (Botany) / The genus Lessertia DC. consists of 54 species of papilionoid legumes. The species have imparipinnate leaves, paired stipules, sub-capitate or elongate racemes and compressed or inflated legumes. The closest relative of the genus is Sutherlandia R. Br. ex W. T.Aiton, which differs in having a very large, bird-pollinated flower, a standard which is smaller than the keel, a long ovary stipe and a very large, much inflated legume. The last comprehensive revision of Lessertia was done by Harvey (1862), where 30 species were recognized. Harvey concluded that the species were difficult to define. This study was therefore initiated to evaluate characters of possible taxonomic value so that the circumscription and identification of species can be facilitated. More than 1000 specimens from different herbaria were examined to study morphological characters such as habit, indumentum, leaves and leaflets, flowers and flowering times, fruits, habitat and distribution of the species. Flowers of all the species were dissected and flower parts were drawn using camera lucida. Flower characters such as the length, width and vestiture of the petals were studied. For flavonoids and terpenoids, 17 species of Lessertia were sampled for a pilot study to compare chemical compounds between the species. The ethnobotanical literature was reviewed in order to compile a list of all the species of value in traditional medicine. Vegetative characters are often not species-specific but they can be used to distinguish between some closely related species, either as single characters or as combinations of characters. Further details can be seen in the keys presented in this study.