Random amplified polymorphic DNA (RAPD) amplified by the polymerase chain reaction (PCR) was used to estimate the relatedness of three biotypes of brown planthopper, Nilaparvata lugens (Stål), from the Philippines. Each individual brown planthopper had a unique set of RAPD bands, but no bands were diagnostic for any one biotype. Brown planthopper types 1, 2 and 3 were genetically homogeneous. This supports results of other studies which conclude that brown planthopper biotypes are not sub-specific categories, but merely represent individual variation for virulence to rice cultivars.