The role of growth factors in the development and spread of head and neck cancers has received little attention. Platelet-derived growth factor (PDGF) is a potent mitogen that is released normally in wound healing, but is also secreted by human malignant epithelial cells. In breast and ovarian carcinomas, elevated plasma PDGF has correlated with a poorer prognosis. This preliminary study was designed 1) to determine if PDGF is elevated in the plasma of patients with squamous cell carcinoma of the head and neck and 2) to determine whether there is any change in levels following surgical ablation. The PDGF was measured by radioimmunoassay in 18 patients with head and neck squamous cell carcinoma and in 12 normal controls. In the control group the mean level was 7.4 fmol/100 microL (range 2.8 to 12.5, median 7.6), in spite of the fact that PDGF is reportedly not measurable in normal subjects. The mean PDGF level in the cancer patients was 20.4 fmol/100 microL (range 4.1 to 35.7, median 20.5) and as compared to the control group was significantly elevated (median two-sample test, p < .001). Of the 20 cancer patients, only 4 had levels less than 12.5 fmol/100 microL. Moreover, 2 of these had undergone prior radiotherapy. In all cases, PDGF levels decreased significantly after surgery. These results support the importance of the further investigation of plasma PDGF levels as a potential biomarker to evaluate efficacy of treatment, possibly to aid in the detection of tumor recurrence, and even to be a potential indicator of tumor aggressiveness.