We established a new evaluation system for metastatic potential of oral squamous cell carcinoma (SCC), utilizing a combined examination of histopathological grades of the carcinomas based on cell differentiation and invasive mode according to Yamamoto's criteria, and the cellular expressions of CD44, E-cadherin (E-cad), heparan sulfate glycosaminoglycan (HS-GAG) and Phaseolus vulgaris leukoagglutinin (L-PHA)-binding oligosaccharides on the carcinomas. Histochemical patterns of expression of these markers were classified into positive (+2), weakly positive (+), and negative (-). The histopathological grades and the histochemical patterns of the SCC were estimated on a 0-2 point scale, i.e. point 2 for poorly differentiated, mode 4D, CD44++, E-cad-, HS-GAG++, or L-PHA++; point 1 for moderately differentiated, mode 4C, CD44+, E-cad+, HS-GAG+, or L-PHA+; and point 0 for well differentiated, mode 1, mode 2, mode 3, CD44-, E-cad++, HS-GAG-, or L-PHA-. As a result, incidence of metastasis in the cases with a total score of more than 6 (62.8%) was significantly higher than that with a total score of less than 5 (9.3%). This evaluation system will yield useful information concerning the prognosis of patients with oral SCC.