Adhesion molecule expression by pulmonary endothelial cells is considered to play an important role in the recruitment of circulating leukocytes to sites of inflammation in the lung. We have used P-selectin- and intercellular adhesion molecule type 1 (ICAM-1)-deficient mice to determine whether these adhesion molecules are important to pulmonary eosinophil recruitment after allergen challenge. There was a significant inhibition of lung tissue eosinophil recruitment in ICAM-1-deficient mice (approximately 84% inhibition compared to wild-type mice) and P-selectin-deficient mice (approximately 67% inhibition compared to wild-type mice) 3 h after allergen challenge. The number of bronchoalveolar lavage (BAL) eosinophils in P-selectin-deficient and ICAM-1-deficient mice was also significantly reduced compared with wild-type mice. Levels of BAL eosinophil peroxidase (EPO) were significantly lower in ICAM-1-deficient mice (0.21 +/- 0.03 EPO units) compared with wild-type mice (3.34 +/- 0.65 EPO units). There was no significant difference in the degree of inhibition of eosinophil recruitment in ICAM-1-deficient mice at the three time points (3, 12, and 24 h) of study after allergen challenge. However, in P-selectin-deficient mice there was a decline in the degree of inhibition of eosinophil recruitment from 3 h (67% inhibition) and 12 h (72% inhibition) postchallenge, to 24 h postchallenge (38% inhibition), suggesting that other adhesion molecules may be playing a more prominent role than P-selectin at later time points. These studies suggest an important role for ICAM-1 and P-selectin in eosinophil recruitment to the lung after allergen challenge.