We measured the levels of soluble intercellular adhesion molecule-1 (sICAM-1) in sera from patients with bronchial asthma. sICAM-1 levels in sera from atopic asthmatic patients in stable conditions were higher than in normal control subjects. Furthermore, the sICAM-1 levels in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. These results suggest that higher levels of sICAM-1 in sera reflect the upregulation of ICAM-1 expression in allergic inflammation.