With the recent demonstration of circulating immune complexes in a variety of malignant and nonmalignant diseases, we have examined the sera of head and neck cancer patients for evidence of soluble immune compleses. Using the Raji, cell test, we have shown that immune complexes are present in over 80% of the cancer sera examined as compared to less than 10% of normal control sera, and that these complexes persist following treatment of the patients by surgery or radiation therapy. These complexes may be acting as blocking factors which would account for the anergic state of these patients.