Three Plumbago spp have been tested for mosquito larvicidal activity. The crude extracts exhibiting the highest larvicidal activity against Anopheles gambiae were hexane (LC50 = 6.4 microg/mL) and chloroform (LC50 = 6.7 microg/mL) extracts from Plumbago zeylanica Linn, chloroform (LC50 = 6.7 ug/mL) extract from Plumbago stenophylla Bull and ethyl acetate (LC50 = 4.1 microg/mL) extract from Plumbago dawei Rolfe. These LC50 values were within 95% confidence limits. 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin) 1 (LC50 = 1.9 microg/mL) and beta-sitosterol 2 were characterised from ethyl acetate extract of root bark of P. dawei, a native medicinal plant growing in Kenya, based on spectral analysis and comparisons with data in literature.