PALAVRAS-CHAVE: Variabilidade genética, pulgão-verde-dos-cereais, relação inseto-plantaABSTRACT -The greenbug Schizaphis graminum (Rondani) is one of the most important cereals pests in the world. Within populations of this species, several biotypes, which are clones that share same virulence relationships with cultivated plants, can be distinguished. Molecular markers have been used to genetically characterize insect populations because they are fast and cost effective. In order to find RAPD markers to identify Brazilian S. graminum biotypes, nineteen clonal populations of three biotypes (B, C and E) from Brazil and three clonal populations from the U.S. were examined. Eighteen primers were used to analyze the material, but only six primers revealed polymorphisms and among those, three produced diagnostic band profiles that allowed biotype characterization. Using Jaccard Similarity Index and UPGMA clustering method it was possible to show that biotype B is genetically very distinct from C and E, which are closely related to each other. The biotype C showed the greatest genetic diversity, while biotype E was the least diverse. Analysis of Molecular Variance (AMOVA) showed that genetic variance among clonal populations belonging to the same biotype is smaller than among clonal populations grouped according to their geographical similarity.