Brush borders, enterocytes, or both preparations obtained from the small intestine of 345 pedigreed pigs, carrying components of seven breeds, were tested by adhesion assay in vitro with 6 3 2 enteropathogenic Escherichia coli strains, each expressing one of the three K88 pilus antigens, K88ab, K88ac and K88ad. With few exceptions, all pigs were classified as belonging to one of four adhesion phenotypes: