The 48 Vero cytotoxin-producing Escherichia coli (VTEC) examined for properties associated with virulence were of human origin and represented 17 O serogroups other than O157 and O26. Only Vero cytotoxin production was common to all the strains. About 60% produced enterohemolysin and hybridized with the CVD419 probe derived from plasmid sequences of E. coli O157. Thirteen strains gave localized adherence (LA) to HEp-2 cells. All of these hybridized with the E. coli attaching and effacing (eae) gene probe and were positive in the fluorescence actin staining test, properties characteristic of strains that efface intestinal microvilli. A further 5 strains were eae probe-positive but did not give LA. None of the VTEC hybridized with a probe specific for the enteropathogenic E. coli adherence factor. Seven strains adhered to HEp-2 cells in a diffuse or aggregative pattern but did not hybridize with probes for these phenotypes. Non-O157 E. coli strains are diverse in their properties, although some may share virulence mechanisms with other diarrheogenic E. coli.