Cellular chemotaxis is the best-known function of chemokine receptors which are closely linked with tumor metastasis. In fact, positive expression of chemokine receptors could also be identified even in some patients without metastatic tumors, while the clinical relevance of this data has not been fully established. Our studies were designed to clarify the CCR4 expression profiles and to explore its potential role in histologically node-negative (pN0) gastric cancer (GC). Immunohistochemistry (IHC) or immunohistofluorescence (IHF) analysis was performed on specimens obtained from 108 patients with pN0 GC. We found that CCR4 was aberrantly over-expressed inpN0 GC tissues, with different expression patterns on tumor cells and being associated with T-stage (P = 0.002). The matrigel in vitro invasion assay revealed that over-expression of CCR4 in GC cell lines significantly enhanced the invasive capacity of these cells. Results from real-time RT-PCR and gelatinzymography showed a significant increase in matrix metalloproteinase (MMP)-9 production induced by the forced expression of CCR4 in GC cell lines. Our data suggest that the aberrant CCR4 expression is involved in tumor invasion of pN0 GC and, conceivably, antagonists of CCR4 might be useful candidates for controlling early events in tumor progression.