Results from pre-treatment SCC antigen assay were assessed in 106 patients with epidermoid carcinoma of the upper aerodigestive ways. The control population consisted of healthy blood donors (N = 61). Blood antigen levels ranged 1.6 ng/ml to 21.5 ng/ml in the patient population. 35 patients in 106 (i.e., 33% of cases) had levels considered pathological (greater than 2.00 ng/ml). Antigen levels were higher with increasing tumor size and when adenopathy was more marked (N+, N+R+). However, no correlation could be found with the T (stage)--N (histological) classification of tumors or with the site of lesion. Tumor immunologic response was obviously not uniform. Although the SCC antigen presents no diagnostic value, it appears to bear some prognostic significance, regardless of the tumoral stage. Antigen levels below 2.00 ng/ml correlate with (p less than 0.001) good immediate therapeutical results. On the other hand, serum levels greater than 2.00 ng/ml correlate either with non-sterilization, or with locoregional recurrence and/or rapid development of metastases. Other studies are required to confirm these data, and to demonstrate the value of long-term SCC antigen monitoring in these patients.