We have demonstrated the possibility that the stromal cell-derived factor-1 (SDF-1; CXCL12)/CXCR4 system might be involved in the establishment of lymph node metastasis in oral squamous cell carcinoma (SCC). In order to further clarify the role of the SDF-1/CXCR4 system in oral SCC, we examined the expression of CXCR4 and SDF-1 in biopsy specimens from 61 patients with oral SCC by means of immunohistochemistry, and investigated several clinicopathological factors, including age, sex, lymph node metastasis, invasion, recurrence and prognosis. The expression of CXCR4 and SDF-1 was observed in 57.3 and 11.4% of our subjects, respectively. Although we were unable to find a statistically significant association between the expression of SDF-1 and any clinicopathological factors, we did find a significant association between the expression of CXCR4 and lymph node metastasis (P=0.0417). Moreover, the mode of invasion (P=0.0002) and recurrence of the tumors (P=0.0185) were strongly associated with CXCR4 expression, and the CXCR4-positive group showed a significantly poorer prognosis than the CXCR4-negative group (P=0.0401). Recombinant SDF-1alpha stimulated in vitro invasiveness and scattering in CXCR4-expressing oral SCC cells, but the treatment did not affect the expression of matrix metalloproteinases or urokinase-type plasminogen activator. These results indicate that SDF-1/CXCR4 signaling in oral SCC cells might be involved in the diverse action of oral SCC, including invasion or micrometastasis at the primary site and lymph node metastasis.