The etiologic relationship of the Epstein-Barr virus (EBV) to nasopharyngeal carcinoma prompted this study of the efficacy of interferon-gamma (IFN-gamma), which possesses antiviral and antitumor activity, in the treatment of recurrent carcinoma. Fourteen patients received recombinant IFN-gamma in daily intramuscular doses of 5-10 X 10(6) U/m2. Of 13 patients evaluable for response, five had a minor response; disease was stable in two and had progressed in six. EBV serology for immunoglobin (Ig) G, IgA-VCA, and early antigen was measured in six patients. In four of these, titers rose consistently with disease progression and in one patient, titers decreased with minor response.