The ability of Escherichia coli strains isolated from various human infections to bind fibronectin (Fn), collagen type I (Cn), laminin (Ln), and vitronectin (Vn) was studied. Binding of the proteins was shown to be specific and to be inhibited after protease treatment and heating of bacterial cells at 80-degrees-C. Binding of Fn, Cn type I, and Ln was not expressed in CFA broth and Voccani's medium with sodium chloride concentration above 0.5%. Fn binding was specifically enhanced for cells grown in CFA broth and Voccani's medium containing CaCl2 (up to 10 mM final concentration), whereas binding of Cn type I was decreased. Growth in liquid medium yielded cells with maximal binding of Fn, Cn type I, Vn, and Ln after 20-22 h of growth. The binding of Fn, Cn type I, and Vn to cells of strain NG7C was inhibited for cells preincubated with antisera raised to the homologous strain; E. coli NG7C cells seem to have specific binding sites for Fn, Cn type I, Vn, and possibly also Ln.