Effects of the aqueous extract of Sphaeranthus senegalensis Vaill. (Family: Compositae) were studied on spontaneous motor activity, exploratory behaviour, rota-rod performance and pentobarbital sleeping time in mice. Preliminary phytochemical evaluation and acute toxicity (LD50) values were also studied. The extract (50 and 100 mg/kg p.o.) produced reduction in spontaneous motor activity, exploratory behaviour and motor coordination and prolonged pentobarbital sleeping time. Glycosides, saponins and tannins were shown to be present in the extract. The i.p. LD50 in mice was 2735.61 and 5000 mg/kg orally. The results suggest that the aqueous extract of S. senegalensiscontains some active principles, which may be sedative in nature.