Brush borders or enterocytes obtained from the small intestine of 248 pedigreed pigs were tested by adhesion assayin vitrowith enterotoxigenicEscherichia(E.). coli strains, each expressing one of the three K88 pilus variants K88ab, K88ac and K88ad. All pigs were classified as belonging to one of the four adhesion phenotypes: I ‐ K88ab(‐), ac(‐), ad(‐); II‐K88ab(‐), ac(‐), ad(+); III‐K88ab(+), ac(+), ad(‐); and IV‐K88ab(+), ac(+), ad(+). Serum or red cells were typed for 15 blood group systems: A‐O, B, C, D, E, F, G, H, I, J, K, L, M, N and O; for 11 biochemical polymorphisms: PI1, PI2, PO1A, A1BG, GPI, PGD, TF, HPX, ADA, PGM and AMY; the polymorphism at the IGHG1 locus. Linkage analysis was performed between the alleles at the locus (loci) specifying K88 receptors able to bind one or more different serological types of K88 E. coli and alleles for markers at other loci. Linkage was demonstrated between the locus for the L blood group system and the locus (loci) for K88E. colireceptors (Ẑ= 3.24), adding one locus (loci) to the previously identified linkage group IV (LGIV) [L‐SLB]. The maximum likelihood estimate of the recombination fraction (0C) was 0.23. No evidence was found for linkage between any of the other biochemical and immunogenetic markers and the receptor lo