The ability of enterotoxigenic strains of E. coli to adhere to immobilized mucosal components prepared from the large and small intestines of mice was examined in vitro. Various strains of E. coli were labeled with ( 3H)-acetate and incubated in tissue culture plates containing immobilized mucosal components or bovine serum albumin. E. coli strains which were positive for K88 or K99 antigen, and one E. coli strain isolated from a human urinary tract infection, were shown to adhere readily to large and small intestinal mucosal preparations, but not to bovine serum albumin. E. coli K-12 and a variety of enterotoxigenic strains isolated from humans, including a CFA/1 positive strain, demonstrated little or no ability to adhere to any of the preparations. E. coli adhesion to the mucosal preparations was shown to be mannose-resistant for all E. coli strains tested, but was inhibited by growth of the organisms at 18°C. Adhesion of each of the K88 or K99 positive strains was inhibited by homologous antiserum, but not by heterologous antiserum or normal rabbit serum. The data indicate that the mucosal preparations employed contain receptors for specific bacterial adhesins, and suggest that the use of such preparations may provide an alternative to the use of whole cells both as a source of receptor and as a means of investigating the adhesive properties of E. coli.