Tumor progression is associated with the clonal expansion of surviving cell variants. These results in cancer cell heterogeneity and selection of cells with a high malignant potential reflected also by the ability to metastasize. In seeding and implantation of cancer cells at the distant site cell adhesion molecules play a crucial role. Of particular interest is CD44 adhesion molecule, which possibly is involved in tumor metastasis development. Forty cases of an advanced gastric cancer were studied. Paraffin block were collected from the files. In addition to routine tumor typing, grading (Lauren and Goseki classifications) and staging, CD44 (standard, v5 and v6) was studied by immunohistochemistry and RT-PCR. CD44 immunoreactivity was found in 36 of the 40 studied cases. A significant overexpression of CD44v5 was noticed in gastric cancer. This was especially seen in Goseki's grades I and III (72.7% of cases) and was less common in Goseki's grades II and IV (44.4% of cases). CD44v6 was less commonly expressed. In some cases CD44 heterogeneity of neoplastic intravascular emboli was noticed and in some other cases stronger expression of CD44 was present in deeper parts of cancer infiltrate. Immunohistochemical expression was mostly in concert with CD44 gene expression as shown by RT-PCR results. Some discrepancies are discussed. These findings are interesting in view of better prognosis and different route of dissemination of Goseki's grades I + III compared with Goseki's grades II + IV of the gastric cancer. We have shown an overexpression of CD44v5 in an advanced gastric cancer, especially in Goseki's grades I and III. This could reflect a different malignant potential and a different route of dissemination of gastric well differentiated adenocarcinomas.