We showed that Escherichia coli strains attach to HeLa cells in two different patterns. In one, the bacteria cover the whole surface of the cell (diffuse adherence), and in the other, attachment is limited to one or a few sites of the cell surface (localized adherence). Among the enteropathogenic strains, serogroups 055, 086, Olilab, 0119, 0125, 0128ab, and 0142 usually showed localized adherence when tested in the presence of Dmannose. Localized adherence was not shown either by E. coli strains isolated from urine or by enteroinvasive and enterotoxigenic E. coli strains. Some of these strains showed diffuse adherence. Some strains of serogroups 055, 0111, and 0119 showed both localized and diffuse adherence in the same preparation. Mannose-resistant adherence was not related to colonization factor antigens.