Expression of intercellular adhesion molecule-1 (ICAM-1) and endothelial-leukocyte adhesion molecule-1 (ELAM-1) on endothelium can be considered a critical early step for leukocyte migration from blood to tissues during inflammatory processes. Increased circulating soluble ICAM-1 (sICAM-1) levels have been found in sera from patients with Graves' disease (GD) with or without ophthalmopathy. Serum soluble ELAM-1 (sELAM-1) levels have not been measured in these patients. The aim of this study was to clarify the behavior of sICAM-1 and sELAM-1 levels in patients with hyperthyroidism due to GD with or with or without ophthalmopathy and in hyperthyroid patients with toxic thyroid adenoma. We studied sICAM-1 and sELAM-1 levels in 130 subjects (age 23-54 yr), grouped as follows: group 1, 30 untreated hyperthyroid GD patients (21 females and 9 males) with active ophthalmopathy; group 2, 26 euthyroid GD patients (16 females and 10 males) with active ophthalmopathy; group 3, 33 hyperthyroid GD patients (22 females and 11 males) without ophthalmopathy; group 4, 11 untreated hyperthyroid patients (7 females and 4 males) with single toxic adenoma; and a control group of 30 healthy subjects (21 females and 9 males). sICAM-1 and sELAM-1 concentrations were measured by a sandwich enzyme linked immunosorbent assay (ELISA) method. Groups 1, 2, and 3 (P < 0.001 for all 3 groups) but not group 4 showed increased sICAM-1 levels compared with the control group. However, groups 1 and 2 (P < 0.001 for both) showed higher values of sICAM-1 than group 3, and group 1 showed higher sICAM-1 levels than group 2 (P < 0.002). Groups 1 and 2 (P < 0.001 for both) but not groups 3 and 4 showed sELAM-1 levels significantly higher than the control group and positively correlated to the severity score of Graves' ophthalmopathy (GO) (P < 0.002 for group 1 and < 0.01 for group 2). Our results confirm that increased sICAM levels in GD patients with or without ophthalmopathy (with higher levels in patients with GO) but not in hyperthyroid nonautoimmune patients may be the consequence of orbital and thyroid inflammation, and they also suggest that sICAM concentrations could reflect the degree of inflammatory activity. Increased sELAM-1 concentrations only, in patients with ophthalmopathy with or without hyperthyroidism significantly correlated to severity score of GO, suggest the measurement of sELAM-1 levels as a specific marker of endothelium activation in GO.