Intercellular adhesion molecule-1 (ICAM-1) plays a crucial role in lymphocyte migration and activation, and is considered important in the pathogenesis of atherosclerosis. K469E is a common polymorphism of the ICAM-1 gene with potential functional significance. The aim of the present case-control study was to evaluate the association between this polymorphism and peripheral arterial occlusive disease (PAOD). ICAM-1 gene polymorphism was examined by polymerase chain reaction and restriction enzyme analysis in 75 Italian subjects affected by PAOD and 227 controls. The distribution of ICAM-1 genotypes in patients affected by PAOD was 32.1% EE, 50.6% EK, and 17.3% KK. The distribution of ICAM-1 genotypes in control subjects was 17.2% EE, 55.1% EK, and 27.7% KK. The EE genotype was significantly more common in patients than controls (P = 0.006). Logistic regression analysis indicated that the presence of the EE genotype significantly increases the risk of PAOD (odds ratio, 3.5; 95% confidence interval, 1.5-8.4; P = 0.004). This is the first study documenting a role of the ICAM-1 gene polymorphism in the pathogenesis of a cardiovascular disease, such as PAOD. Our data support the hypothesis that inflammatory mechanisms are important in the pathophysiology of vascular diseases with an atherosclerotic basis.