Past studies have shown that carbohydrate residues reactive with the Griffonia simplicifolia isolectin B4 (GS I-B4) are present on the surface of highly-malignant murine sarcoma cells but are lacking or expressed in much lower amounts on the surface of low-malignant cells isolated from the same parent tumors (Am J Pathol 111: 27; J Nat Cancer Inst 71: 1281). In the present study it is shown that an antibody which recognizes the trisaccharide Galalpha1-3Galbeta1-4GlcNAc- is reactive with the highly-malignant cells but is non-reactive with the low-malignant cells. Further studies show that the high-malignant cells not only bind GS 1-B4 but also bind Evonymus europaea lectin (which like GS I-B4 recognizes terminal galactose in alpha1-3 linkage) and Erythina crystagalli lectin (which recognizes sub-terminal galactose in the beta1-4 linkage--e.g., Galbeta1-4GlcNAc). In contrast, the low malignant cells bind Erythina crystagalli lectin as efficiently as the high malignant cells but do not bind (or bind much smaller amounts of) either GS I-B4 or Evonymus europaea lectin. The present studies also show that there is no significant difference between high- and low-malignant cells in expression of alpha-galactosidase activity. In contrast, the high-malignant cells express high levels of alpha-galactosyl transferase activity while this enzyme is virtually undetectable in low-malignant cells. Taken together, these studies indicate that differential expression of a single monosaccharide residue distinguishes high- and low-malignant murine sarcoma cells. These studies also identify a mechanism to account for surface carbohydrate differences between the high- and low-malignant cells.