Malnutrition is reported to occur in approximately 30% of head and neck cancer patients. Also, impaired immunocompetence is described as a common phenomenon in this patient group. The purpose of this study was to assess the possible relationship between malnutrition and some prognostically important immune parameters in head and neck cancer patients. Thirty-two malnourished (recent weight loss ≤ 10%) and 34 well-nourished patients undergoing curative treatment for advanced head and neck cancer were studied prospectively, and six parameters of their immune status (leucocytes, lymphocytes, lymphocyte phenotyping, monocytes, HLA-DR expression on monocytes and serum interleukin-10) were determined on the day of panendoscopy. Reference values for monocytes, HLA-DR expression and interleukin-10 were obtained from 43 healthy controls. Although the number of monocytes was elevated in both patient groups, the HLA-DR expression on these monocytes was significantly lower in the malnourished than in the well-nourished and control groups. Tumor stage, tumor localization, recurrence after initial radiotherapy, age and gender were not correlated to HLA-DR expression. No relationships emerged between nutritional status and lymphocyte subsets. Malnourished head and neck cancer patients show a significantly lower HLA-DR expression on monocytes than well-nourished ones and healthy controls. According to the literature this would imply an increased risk for postoperative complications. Indeed, postoperative complications occur more frequently in malnourished than in well-nourished patients.