To determine whether a link exists between the recruitment of inflammatory cells in the airways on a bronchial and bronchoalveolar level and the development of allergen-induced increase in bronchial hyperresponsiveness after allergen challenge, we used bronchial lavage and bronchoalveolar lavage to assess the airway responses to allergen. Twelve symptomatic atopic asthmatics were studied. In all patients bronchial and bronchoalveolar lavage was performed before, 3 h, and 24 h after allergen challenge. Monoclonal antibodies were used directed against T cells (CD3, CD4, CD8) and the eosinophil cationic protein (EG2). Eight patients showed a dual asthmatic response; four patients showed only an early asthmatic reaction after allergen challenge. Clear differences were found between bronchial and bronchoalveolar lavage. Activated eosinophils (EG2) were significantly increased both at 3 h (p = 0.01) and 24 h (p = 0.005). The number of activated eosinophils was significantly higher in the dual responders. A correlation was observed between the severity of the late asthmatic reaction (LAR) and the number of epithelial cells in the bronchial recovery at 3 h, but not at 24 h, in patients who clinically developed a LAR. No significant changes in the number of CD3, CD4, and CD8 cells 3 and 24 h after the challenge both in the bronchial and bronchoalveolar recovery were observed. We conclude that the number of activated eosinophils in bronchial lavage is associated with the development of the LAR and allergen-induced increase in bronchial hyperresponsiveness.