The level of IgM antibodies to the Thomsen-Friedenreich hapten (TF) relative to the total IgM level in the blood sera of gastric and breast carcinoma patients and healthy persons was determined using enzyme-linked immunosorbent assay. The following TF glycoconjugates were tested: TF-polyacrylamide (PAA)(with 10 mol.% of TF hapten Gal beta 1-3GalNAc alpha 1-O(CH2)3NH per number of monomeric units in the polyacrylamide), TF-human serum albumin (HSA)(Gal beta 1-3GalNAc alpha 1-O-p-C6H4-HSA containing approximately 15 carbohydrate residues per HSA molecule), asialo-kappa-caseinoglycopeptide, and asialoglycophorin. The total IgM level was determined using antibodies to the mu-chain of human IgM. The statistically significant difference between cancer patients and healthy donors was revealed with two conjugates: TF-PAA and TF-HSA. In the case of TF-PPA, the sensitivity of the assay was 75-83%, and the specificity was 77%. Thus, TF-PAA is the most suitable conjugate for measuring the level of serum anti-TF-IgM antibodies.