Bovine enterotoxigenic Escherichia coli (ETEC) carrying F17a fimbriae attach to the intestinal epithelium by means of the F17a-G adhesin. Since filamentous bacteriophages can be employed for the display of foreign peptides, we tested the applicability of this system to F17a-G. The receptor-binding domain of the F17a-G adhesin was expressed on bacteriophage M13, as an amino-terminal fusion with the phage protein pIII. This domain retained its N-acetyl-beta-D: -glucosamine binding activity. The phage presenting the fimbrial receptor-binding domain elicited an IgG response against F17a-G after intraperitoneal immunisation of mice.