Intercellular adhesion molecule-1 has been implicated in tumor progression and metastasis. Like soluble forms of other membrane receptors, a circulating form of intercellular adhesion molecule-1 (sICAM-1) has been identified in the serum of healthy subjects and it has been found in malignant diseases at increased levels. This study evaluated the serum concentration of sICAM-1 in 112 patients with non-small cell lung cancer (NSCLC). Soluble ICAM-1 levels were significantly higher in all patients when compared with the controls; serum concentration of sICAM-1 correlated with clinical stage and tumor progression. These results suggest that elevated levels of serum ICAM-1 could be of prognostic importance in patients with NSCLC.