Isolates of Fusarium oxysporum f.sp elaeidis from Zaire and Brazil and F. oxysporum from Malaysia were characterized by DNA restriction fragment length polymorphisms (RFLPs), pathogenicity and for vegetative compatibility as determined by nitrate non-utilizing (nit) mutants. There was complete correlation between all three characteristics for isolates from Brazil and good correlation between pathogenicity and vegetative compatibility for Zairean isolates. A complex relationship between vegetative compatibility and RFLP group was demonstrated for these latter strains. Two distinct VCGs occurred in Zaire and Brazil but non-pathogenic Malaysian isolates showed a high degree of genetic diversity for vegetative compatibility and RFLP analysis as did four non-pathogenic strains from Zaire. The findings are discussed with regard to developing a rapid method for distinguishing pathogenic from non-pathogenic strains of F. oxysporum and to understanding the origin and spread of oil palm wilt.