Recent studies have suggested that intercellular adhesion molecule-1 (s1CAM-1) may be involved in the pathogenesis of asthma. In addition. a soluble form of sICAM-1 has been detected in increased concentration in the sera ofpatients with certain inflammatory conditions. To determine whether bronchial asthma is associated with increased levels ofsICAM-1 in the serum and bronchoalveolar lavage (8AL) and to assess the effects of therapy on these levels. the concenfrations ofsICAM-1 were measured in the sera and BAL of20 healthy subjects. 20 patients with extrinsic asthma during attack and remission after 2 weeks of treatment without steroid (group I). 20 patients with intrinsic asthma during attack and remission after 2 weeks of treatment without steroids; (group II) and 20 patients with extrinsic asthma during attack and remission after 2 weeks of treatment including corticosteroids (Group III). The mean (± SD) ofserum sICAM-1 in healthy subjects was 210.2 ± 67.2 nglml but in extrinsic asthma during attack was 387.8 ± 67.5 nglml (P < 0.005) and during remission was 261.7 ± 81.4 nglml (P < 0.05). In the infrinsic asthma during attack was 315.6 ± 59.8 nglml (P < 0.005) and during remiSsion was 248.3 ± 79.4 nglml (P < .05). In group III during attack was 392.1 ± 80.9 nglml (P < 0.005) and during re- I' mission after 2 weeks of treatment including steroids was 216.7' ± 84.9 nglml (P > 0.05). The mean (± , SD) ofsICAM-1 in the BAL ofhealthy subjects was 213.9 ± 72.6 nglml but in group I was 268.4 ± 112.3 nglml (P < 0,05). in group II was 256.7 ± 82.6 nglml (P < 0.05) and in group IlIlVas 221.4 ± 92.6 ngl ml (P > 0.05). There was significantly negative correlation between serum sICAM-1 ill all asthmatic . patients during attack and (forced expiatory volume in the first second) FEV 1% ofpredicted. Also there was no correlation between level of serum slCAM-1 and IgE level but there was significantly positive correlation between semm sICAM-/ and count of blood eosillophils. Thus active bronchial asthma is associated with the presence of increased levels of serum and bronchoalveolar lavage sICAM-1 and these levels may be modulated by treatment specially corticosteroid therapy.