The 4F2 antigen is a cell-membrane glycoprotein which arises early in the G0-G1 phases of the cell cycle. This molecule is present in all established human cell lines and most malignant human cells. The authors used an indirect immunophosphatase method to study 50 squamous cell carcinomas of the larynx and ten lymph-node metastases, corresponding to six primary tumors, for 4F2 expression. The tumors showed several patterns of 4F2 staining which were correlated with different behaviors and prognoses of the neoplasms. Three different patterns (no staining, peripheral staining, and diffuse 4F2 expression) are described as are their relationships with metastatic behavior of the carcinomas. Tumors with metastases were found only in the third group (P = 0.0001). These results led to the following conclusions: (1) the 4F2 antigen is present in squamous cell carcinomas; (2) its distribution reflects the tumor-spreading pattern; and (3) it correlates with differentiation and metastatic behavior.