It has already been demonstrated in human and animal systems that PGE2 is a suppressor signal for many immune functions. These include T-lymphocyte blastogenesis, natural killer cell activity, and cytolytic T-lymphocyte activity. These functions are important for destruction of tumor cells. Conceivably, suppression of these functions by excessive PGE2 restricts tumor cell kill, and reversal of suppression by an inhibitor of prostaglandin synthesis such as indomethacin could increase tumor cell kill. The purpose of this study was to determine the kind of prostaglandins (PGs) produced by tissues with squamous cell carcinoma of head and neck and to measure the concentrations of PGE2, 6-keto-PGF1 alpha, and thromboxane (Tx) B2 in the tumor tissue and in the corresponding control tissue. Tumor and normal control tissues at the margin of the resection were obtained from surgical specimens. The production of PGs was determined by incubation of tissue homogenates with 14C-arachidonic acid, by thin layer chromatography, autoradiography, and scintillation counting. Concentrations of PGs were measured by radioimmunoassay. Tumor tissues produced PGD2, E2, TxB2, F2 alpha, and 6-keto-F1 alpha, and 15-, 12-, and 5-monohydroxyeicosatetraenoic acid (HETE). Concentrations of PGE2 were four times higher in the tumor tissues compared to those in control tissues. There was no difference between the levels of TxB2 and 6-keto-PGF1 alpha in the tumor tissues and those in control tissues. The results of this study will serve as basic information necessary for the potential use of inhibitors of PG-synthesis in the treatment of head and neck carcinoma.