Strains of enteropathogenic Escherichia coli (EPEC, 157 strains), enterotoxigenic E. coli (ETEC, 10 strains), enteroinvasive E. coli (EIEC, 40 strains), enterohaemorrhagic E. coli (EHEC, 10 strains), and enteroadherent E. coli (EAEC, 6 strains), all isolated from children and adults with diarrhoea, uropathogenic E. coli (25 strains) and faecal E. coli (36 strains) isolated from healthy persons were tested for binding to subepithelial connective tissue proteins, viz. fibronectin, collagen and vitronectin (S-protein). Strains expressing high and moderate binding to these proteins were found in all groups including normal stools. The highest incidence of binding strains were found among EAEC, EHEC and EPEC strains. Many strains bound collagen only whereas no strain bound vitronectin only. Binding to these proteins was generally best expressed after overnight growth on CFA agar at 37 degrees C. It is not correlated to surface hydrophobicity, and it is not influenced by O antigens or K1 and K5 antigens. The presence of fimbrial adhesins on extraintestinal isolates did not enhance the binding to soluble form of the matrix proteins. During pathological conditions when subepithelial connective tissue proteins are exposed, strains with the ability to bind fibronectin, collagen and/or vitronectin may have a selective advantage to colonize the tissue.