Chemokines are involved in human hepatocellular carcinoma (HCC) carcinogenesis. However, the exact mechanism of chemokines in HCC carcinogenesis remains unknown. Here we investigated the roles of chemokine receptor 4 (CXCR4) and chemokine ligand 12 (CXCL12) in the metastasis of HCC. We found that the expression levels of CXCR4 mRNA in HCC tissues, MHCC97 cells, and HUVEC cells were 2.52 +/- 1.13, 2.34 +/- 1.16 and 1.63 +/- 1.26, respectively and that the CXCR4 protein levels were 1.38 +/- 0.13, 1.96 +/- 0.32 and 1.86 +/- 0.21, respectively. In contrast, CXCR4 was not detected in normal hepatic tissues. In 78 HCC patients, we also found that the concentration of CXCL12 in cancerous ascitic fluid was 783-8,364 pg/ml and that CXCL12 mRNA level in HCC metastasis portal lymph nodes was 1.21 +/- 0.87 but undetectable in normal hepatic tissues. Finally we discovered that recombinant human CXCL12 could induce MHCC97 cells and HUVEC cells to migrate with chemotactic indexes (CI) of 3.9 +/- 1.1 and 4.1 +/- 1.6, respectively. Cancerous ascitic fluid could also induce the migration of MHCC97 cells with a CI of 1.9 +/- 0.8. Thus, our data suggest that CXCR4 and CXCL12 may play an important role in the metastasis of HCC by promoting the migration of tumor cells.