Increased expression of sialyl Lewis X or A antigens on metastatic cancer cells leads to their selectin-mediated extravasation. Profound fucosylation of the serum microenvironment may be a factor that interrupts adhesion and influences the formation of metastases. In this study we quantitatively analyzed fucosylation of serum glycoproteins in small-cell and non-small-cell lung cancer patients. Fucosylation of four chosen glycoprotein bands was measured as the reactivity with Aleuria aurantia lectin on nitrocellulose blots, preceded by polyacrylamide gel electrophoresis. Relative fucosylation and fucosylation coefficients were calculated by densitometric analysis. Fucosylated oligosaccharides were observed in higher amounts in cancer sera when compared to sera from healthy individuals in all bands analyzed. Glycoproteins of a molecular mass of 29 kDa appear to carry more fucose residues than the 42-kDa band, comprising alpha(1)-acid glycoprotein and haptoglobin. Glycans of the 26-kDa band were fucosylated to a higher extent in non-small-cell vs. small-cell lung cancer. The results suggest that the extent of fucosylation could be a useful marker for estimation of the glycosylation status of serum proteins in cancer patients. Cluster analysis leads to the preliminary suggestion that the fucosylation status could serve as a predictive factor for patient survival.