We investigated the variable adhesiveness of pancreatic cancer cells by glycosylation inhibitor to elucidate the role of carbohydrate antigens in cell-cell and cell to extracellular matrix adhesion. Various carbohydrate antigens were strongly expressed on pancreatic cancer cell (SW1990) by ELISA, and these expression correlated to its in vitro invasiveness and in vivo metastatic potential. Cellular adhesion to Matrigel, laminin and collagen type IV and homotypic cellular aggregation in SW1990 were enhanced by reducing O-linked glycosylation with its inhibitor (Bzl-GalNAc), and these effect were reversed by additional purified mucins. These results suggested that O-linked glycoproteins on SW1990 cell surface may inhibit its adhesiveness to the substratum and aggregation properties by hindering surface receptors, and this variability of adhesiveness induced by altered glycosylation may have an another important role in highly metastatic potential of well glycosylated cancer cells.