Changes in monocyte and macrophage function have been demonstrated in patients with head and neck squamous cell carcinoma. The purpose of this study was to evaluate tumor necrosis factor (TNF) production by activated monocytes from patients with head and neck squamous cell carcinoma and to evaluate its relation to cancer stage, weight loss, and performance status. Monocytes from patients (n = 10) and controls (n = 10) were isolated from peripheral blood mononuclear cells by plastic adherence and incubated with lipopolysaccharide (10 micrograms/mL). The TNF concentration of supernatants was assayed by TNF alpha-specific immunoassay. The TNF production by monocytes from head and neck squamous cell carcinoma patients was significantly higher (P less than .001) than those of controls. No significant relationship was found to cancer stage, weight loss, and performance status. These findings indicate that, in head and neck squamous cell carcinoma patients, an increased TNF production by activated monocytes takes place which does not correlate with cancer stage, cancer-related weight loss, and performance status.