Since various experimental findings point towards an important role of cell surface carbohydrates - in particular sialic acid - in cancer metastasis, the rationale of this study was to look for possible differences in carbohydrate metabolism and glycoprotein expression in well-defined related tumor lines of different metastatic capacity. The tumor lines analyzed were L5178Y E (= Eb), a low-metastasizing, methylcholanthrene-induced lymphoma of a DBA/2 mouse, and L5178Y ES (= ESb), a spontaneous high-metastatic variant thereof. A non-related, highly metastasizing tumor, MDAY-D2, and ConA-stimulated spleen cells were included in the study. These cell lines were compared for incorporation rates of various labelled carbohydrates and for glycoprotein patterns in SDS-polyacrylamide gels. Marked differences were observed in the incorporation of 3H-fucose, while the incorporation of 3H-galactose and 3H-mannose was similar in the different cell lines studied. Only the metastatic variant ESb incorporated 3H-fucose at a rate similar to that of ConA-stimulated T-cell blasts. Eb cells did not incorporate 3H-fucose while MDAY-D2 had a significantly lower 3H-fucose incorporation rate. Separation and purification of the intracellular products of 3H-fucose by gel filtration and high-voltage electrophoresis revealed in Eb cells a block in the synthesis of fucosylated glycoproteins at the step of the fucose-I-P-guanylyltransferase. No apparent defect in the fucose pathway was detectable in MDAY-D2 cells. An Eb----ESb shifted cell line regained the ability to incorporate 3H-fucose. All tumors displayed unique glycoprotein patterns in SDS-PAGE. Labelling with 3H-mannose revealed the most distinct bands, while labelling with 3H-galactose gave fewer and broader bands. Although clonal instability of metastasizing tumor variants has been frequently reported, subclones of Eb and ESb showed characteristics similar to those of the original cell lines with regard to metastatic capacity, fucose metabolism and glycoprotein expression. These results will be discussed in relation to differences in fucose metabolism and in surface expression of fucose as observed in other tumor systems consisting of high- and low-metastatic lines.