Wheat germ agglutinin was found to agglutinate cells of Escherichia coli PAT 84, Micrococcus luteus, Staphylococcus aureus H, and of S. aureus 52A5, but not cells of S. aureus 52A2. Interaction of wheat germ agglutinin with a soluble linear peptidoglycan secreted by Micrococcus luteus and with the teichoic acid of S. aureus H was demonstrated by agar gel diffusion, quantitative precipitation and inhibition of hemagglutination of trypsinized rabbit erythrocytes. No interaction could be demonstrated with the teichoic acid from a phage-resistant mutant (S. aureus 52A2) which lacks A-acetyl-D-glucosamine residues. All interactions were specifically inhibited by low concentrations of chitotriose (GlcNAcbeta1 leads to 4GlcNAcbeta1 leads to 4GlcNAc) and the bacterial cell wall tetrasaccharide, GlcNAcbeta1 leads to 4MurNAcbeta1 leads to 4GlcNAcbeta1 leads to 4MurNAc. Hemagglutination-inhibition experiments showed that the linear peptidoglycan and the teichoic acid of S. aureus H were several thousand times more potent inhibitors of wheat germ agglutinin than was N-acetyl-D-glucosamine. Comparison of the efficiency of different saccharides in inhibition of hemagglutination and precipitation of polymers by wheat germ agglutinin, strongly suggests that secondary, non-specific interactions contribute to the binding of the lectin to the polymers.