The effects of a cutting trial, conducted to study the combined influence of defoliation and competition from surrounding vegetation on the vigour ofThemeda triandraandAristida junciformis, were evident after the single season of treatment implementation.Aristida junciformiswas more sensitive to defoliation thanT. triandra, whereas competition reduced yield to a greater extent inT. triandrathan inA. junciformis. The two species differed in their ability to tolerate defoliation under competition. Defoliation reduced the yield of A.junciformis, at all levels of competition, to a greater extent thanT. triandra. Aristida junciformiswas particularly sensitive to a combination of severe defoliation and full competition. It is suggested that manipulation of grazing patterns may shift the competitive balance between palatable (e.g.T. triandra)and unpalatable (e.g.A. junciformis)components of the sward.