Background: A rapid increase in leukocyte adhesion to endothelium is one of the earliest events in response to inflammation and in the pathogenesis of vascular damage. Vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) are members of the immunoglubulin gene superfamily that play a major role in the leukocyte adhesion process. We assessed the effect of treadmill exercise on circulating soluble form of VCAM-1 and ICAM-1 in patients with intermittent claudication.Methods: In 12 claudicants and 8 age-matched control subjects, venous plasma levels of VCAM-1 and ICAM-1 were determined by sensitive ELISA tests at rest, at maximal tolerated exercise and 5, 15 and 30 rnin after exercise. Patients were selected who did not present any condition known to interfere with adhesion molecule modulation.Results: In controls, exemise did not affect plasma levels of adhesion molecules. VCAM-1 was 610 +/- 42 ng/ml at rest and 592 +/- 53 ng/ml at peak exercise. The corresponding values for ICAM-1 were 232 +/- 17 and 233 +/- 21 ng/ml. Conversely, all claudicants showed increased plasma levels of both VCAM-1 and ICAM-1 at maximal tolerated exercise. VCAM-1 increased from 691 +/- 65 to 832 +/- 83 ng/ml (p < 0.05), ICAM-1 returned from 249 +/- 20 to 275 +/- 22 ng/ml (p < 0.01). Thirty minutes after exercise, VCAM-I and ICAM-1 returned to resting values, being 709 +/- 70 and 244 +/- 21 ng/ml, respectively. No relationship was found between plasma values of adhesion molecules and treadmill performance.Conclusion: In patient with intermittent claudication, exercise increase plasma levels of VCAM-1 and ICAM-1. This probably reflects endothelial activation or damage and thus may have potential implications on the pathophysiology of the arterial disease.