Concern over the use of prophylactic antibiotics and the potential of them being banned has increased interest in other methods of controlling disease. Specifically postweaning diarrhoea in the pig, often associated with E Coli (F4 K88ac) is a candidate for an alternative strategy. If in-feed additives can be demonstrated which effectively block the binding of the F4 (K88)ac pilli to the surface of the pig enterocytes then the severe form of the disease could be controlled without the use of antibiotics. The work reported here provides a screening method to determine whether potential in-feed additives can block the binding of purified F4(K88)ac to isolated brush border membranes taken from neonatal F4(K88)ac positive pigs.