The carbohydrate specificity of 57 MAbs submitted to the ISOBM TD-4 Workshop on MUC1 were investigated by two versions of ELISA, direct binding and inhibition of binding. The following free saccharides and their polyacrylamide conjugates (Sug-PAA) were used: tetrasaccharides--SiaLe(x), Sia--Le(a); trisaccharides--Le(x), 3'HSO3Le(x), Le(a), 3'HSO3Le(a), 3'SiaLac, Atri, Btri; a number of disaccharides including TF, Hdi, SiaTn, LactNAc, and monosaccharides. It was shown that MAbs 143 and 167 interacted only with SiaLe(x), MAbs 127 and 128 only with Le(x). Antibodies 123 and 164 interacted preferably with Le(a) but also recognized Le(c). Antibody 151 recognized alpha GalNAc (Tn) and cross-reacted with beta GalNAc. Antibody 157 displayed high affinity to Atri and Atetr (type 1). Neither anti-TF nor anti-SiaTn antibodies were revealed.