The serum--SCC antigen levels of patients with head and neck tumors were studied prospectively to determine their value in the initial diagnosis of head- and neck-cancer patients. Serum concentrations above 2 ng/ml are considered abnormal. Preliminary results of the study after a 12-month period have been reported elsewhere (1). The final results of the study show an increased percentage (53%) of pathologic findings, mostly due to the increasing number of advanced stage tumors. High serum levels were found in 60% of the T4-tumors (Fig. 4a). Well differentiated carcinomas seem to be associated with the antigen more frequently than poorly differentiated tumors (Fig. 5). SCC antigen levels were examined as many as five times before the start of treatment (85 patients), and in one-third of those cases the differences between the serum levels exceeded 1 ng/ml. As far as 85% specificity is concerned, the ROC-curve shows a sensitivity of only 40% (Fig. 2) which, in addition to the fact that the antigen was most frequently found in cases of advanced tumors, indicates that the usefulness of the SCC antigen as a tumor marker for head and neck cancer must still be regarded as low.