A new delimitation is proposed for three of the sections (Pyramidatae Munir, Spicatae Munir and Verticillatae Munir) of the genus Dicrastylis Drumm. ex Harv. Keys are given to the five sections of the genus and to the 15 Western Australian species of sections Pyramidatae and Spicatae. Four new species from the arid and semi-arid zones of Western Australia are described as Dicrastylis cundeeleensis Rye, D. kumarinensis Rye, D. mitchellii Rye and D. subterminalis Rye. Dicrastylis petermannensis Munir is reduced to a synonym of D. gilesii F.Muell., D. microphyllum Munir to a synonym of D. flexuosa (W.R.Price) C.A.Gardner, and D. georgei Munir is tentatively treated as a synonym of D. cordifolia Munir. None of the previously published subspecies, varieties and forms for any members of the genus is recognised formally here. However, further study of several species complexes occurring in the arid zone is needed as they are extremely variable and taxonomically difficult.