Soluble intercellular adhesion molecule-1 (s-ICAM-1) was measured in the sera of 131 patients with primary and 50 patients with recurrent squamous cell cancer of the head and neck (HNSCC). 30 patients with benign ear, nose and throat diseases served as controls. s-ICAM-1 levels in serum are high in patients with HNSCC, particularly in the advanced tumor stages (UICC IV). Highest levels can be measured at the time of tumor recurrence and locoregional lymph node metastases. The sensitivity (95% specificity) of s-ICAM-1 (cutoff-level: 473 ng/ml) is 4% at primary diagnosis and 12% for recurrent disease. A coefficient of correlation for s-ICAM-1 in combination with SCC, carcinoembryonic antigen and CYFRA 21–1 indicates that no correlation can be found of s-ICAM-1 compared with traditional tumor markers. Due to overlapping values in control and patient groups s-ICAM-1 is not suitable for a specific clinical use in HNSCC.