Serologic tumor markers have been evaluated in the diagnosis, management and follow-up of patients with head and neck cancer. However, to the authors' knowledge no tumor marker has yet been shown to be useful for monitoring the response to chemotherapy in this type of disease, in particular for undifferentiated tumors. The pretreatment levels of CEA, TPA, SCC and ferritin were evaluated in 98 patients with advanced head and neck cancer. Of this group 64 patients were studied sequentially every month during planned chemotherapy and three weeks after treatment using standard commercial kits. The results showed the following sensitivity values: TPA 50%, CEA 36%, SCC 34% and ferritin 19%. The incidence and magnitude of the marker elevations were correlated with the extent of disease. In patients with squamous cell cancer SCC and CEA were elevated (by 68% and 54%, respectively) in tumors with good differentiation (G1), but only by 13% (both markers) in tumors classified as poorly differentiated (G3). CEA, SCC and ferritin serum levels were not correlated with response to chemotherapy, while TPA values correlated with the clinical response to treatment in 100% of patients with undifferentiated cancer and in 75% of those with squamous cell cancer. Our data indicate that in patients with head and neck cancer TPA appears to be a sensitive marker, followed in decreasing order of sensitivity by CEA, SCC and ferritin. However, SCC and CEA seem to be the most suitable markers for squamous cell cancer and in particular for more differentiated tumors (G1). Finally, TPA has proved to be a useful marker for monitoring the response to chemotherapy in patients with head and neck cancer, in particular for undifferentiated tumors.