Resistance to various levels of vancomycin and susceptibility to teicoplanin in enterococci (VanB phenotype) is mediated by the vanB gene cluster. VanB-type resistance was transferred by intra- and inter-specific conjugation between different strains of Enterococcus. Analysis of SfiI-digested genomic DNA by zero integrated-field electrophoresis followed by Southern hybridization revealed vanB-containing chromosomal insertions of approximately 90-250 kb in the transconjugants. Thus, transfer of VanB-type resistance is associated with the movement of large genetic elements from chromosome to chromosome.