Antibodies formed in rabbits to synthetic glycoproteins with the disaccharide structure beta-D-Gal-(1-3)-D-GalNAc, the carbohydrate moiety of desialylated glycophorin A, were investigated for their carbohydrate specificity by hemagglutination techniques and radioimmunoassay. The synthetic disaccharide was coupled to human serum albumin as carrier protein using different spacer groups and different configurations of the disaccharide spacer linkage. Radioimmunological inhibition experiments using a number of different derivatives of the carbohydrate group as inhibitors revealed a significant specificity of the antibodies for the oligosaccharide structure. However, the nature of the conjugation of the disaccharide to the carrier protein was found to be important for defining the specificity of the antibodies. Furthermore the arrangement of the hapten groups in the synthetic antigen had an important influence on the antigen-antibody reaction. No cross-reactions were observed between asialo-glycophorin A and the different synthetic antigens. Synthetic antigens provide a valuable tool for generating carbohydrate-specific antibodies. However, if the synthetic hapten molecule is small compared to the combining site of antibodies, the specificity of the immunological reaction is significantly influenced by the synthetic spacer arm or even the carrier protein.