Objective: To study the expression of CD44 correlation with the ability of metastasis of tumor cells in gastric carcinoma, to find the correlation of the concentration of soluble CD44 Variant 6 (sCD44v6) and the histologic expression of CD44 Variant 6 ( CD44v6 ) in tumors with the clinico-pathologic features, and to make serum concentration of the CD44v6 and the expression of CD 4 4v6 nay be useful an indicator as an early diagnosis, invasion, metastasis, and prognosis. Methods: Serum samples were obtained from 70 patients with primary gastric carcinoma before surgery and 20 patients after surgery. Serum levels of CD44v6 were determined with a quantitative-enzyme-linkimmuno-adsorbent assay. The expression of CD44v6 in tumors was examined by immuno-histo-chemical staining. Results: Both the serum concentration of CD44v6 and its expression in tumors were positively related to the depth of invasion of the tumor, lymph node metastasis, clinical stage, and diffuse type gastric carcinoma, but not to the tumor size. The serum level of CD44v6 in patients with gastric cancer was significantly higher than that in control. The serum concentration of CD44v6 was markedly lowered after curative surgery ( P＜ 0. 001), and the serum level of CD44v6 was higher in patients with gastric cancer with CD44v6 positive tumor cells than in those with CD44v6 negative tumor cells. The serum level of CD44v6 was a prognostic indicator in patients with diffuse type gastric carcinoma, as was the histological expression of CD44v6. Conclusion: CD44v6 of gastric cancer and serum concentration of CD44v6 seems to be correlated to the progression of diffuse type gastric carcinoma metastasis and clinical stage. An elevated level of sCD44v6 may serve as an indicator of lymph node metastasis(especially early metastasis) and bad prognosis in patients with gastric carcinoma.