K88ab pill bound to pig brush border membrane polypeptides with molecular weights of 61,500 and 57,000 and other numerous polypeptides. Periodate treatment decreased binding of both K88ab pili and concanavalin A to brush border membrane polypeptides. Carbamylation and reductive methylation of brush border membrane decreased binding of K88ab but did not affect binding of concanavalin A. The sow colostral whey traction rich in immunoglobulins inhibited bindind of K88ab pili to brush border membrane. K88ab pili bound to sow colostral immunoglobulins and human serum immunoglobulin G in immunoblot assay and dot blot assay. Carbamylation of brush border membrane and immunoglobulins and addition of galactosamine inhibited binding of K88ab pili in dot blot assay. The results suggested that binding of K88ab pili to brush border membrane and immunoglobulin is similar and depends on amino groups as well as carbohydrates in the bonding site.