The capacity to modulate host response against metastatic head and neck cancer may eventually lead to improved survival. This phase II study in patients with advanced head and neck cancer evaluated the efficacy of combination systemic recombinant interleukin-2 (IL-2) and interferon-alpha (INF-a) and evaluated laboratory correlates between tumor response and a) tumor differentiation and b) NK cell activation. Five of fourteen patients responded; two had partial responses and three had transient responses (one complete and two partial, each lasting less than four weeks). Patients that responded had relatively lesser tumor burden and poorly-differentiated metastases. No response was observed in those few individuals in whom natural immune function was only minimally enhanced by therapy. Major toxicity, including but not limited to fever, fatigue and pulmonary compromise, allowed only 3 of 14 patients to complete three cycles of therapy. This preliminary phase II study shows that combination IL-2/INF-a therapy has clinical anti-tumor activity and that the level of NK cell activation and the degree of tumor differentiation may correlate with response.