The 55 antibodies submitted to the ISOBM TD-4 Workshop were analysed for their reactivity with core proteins of the heavily glycosylated MUC1 mucins from the colon carcinoma cell line COLO205 and bile. Both these mucins (designated as H-CanAg and SBG2) are highly glycosylated having 15 and 50 sugar residues per oligosaccharide, respectively. Only a few of the antibodies (129, 139, 153 and 162) reacted with both SBG2 and H-CanAg, and not with a control mucin (L-CanAg) having a similar glycosylation as H-CanAg. These antibodies were tested for their ability to catch soluble mucins, and the antibody 162 was found to be good also in this type of assay. The antibodies selected here should be useful for the detection of high glycosylated forms of the MUC1 mucin in tissues and serum.