We have compared the bronchoalveolar lavage fluid (BAL) cellular composition and the BAL cell lysate histamine content (fluorometric assay) in 28 stable mild to moderate asthmatics (atopic n = 18 and intrinsic n = 10) and 11 control subjects. When compared to control subjects, the whole group of asthmatics had a higher proportion of BAL eosinophils (p < 0.01) and metachromatic cells (p < 0.05). The BAL cell lysate histamine was increased in atopic (p < 0.05) and intrinsic asthmatics (p < 0.05) in comparison with control subjects. In the whole group of asthmatics, the BAL cell lysate histamine content correlated with the percentage of BAL eosinophils (r = 0.58, p < 0.01). This relationship was significant in both atopic (r = 0.48, p < 0.05) and intrinsic (r = 0.70, p < 0.05) asthmatics. For the whole group of asthmatics, both the BAL cell lysate histamine and the percentage of BAL eosinophils inversely correlated with the percent predicted FEV1 (r = -0.42, p < 0.05; r = -0.51, p < 0.05). We conclude that an increased BAL cell lysate histamine content correlates with airway eosinophilic infiltration and lung function impairment in mild to moderate atopic and intrinsic asthmatics. This suggests that BAL mast cells play a key role in recruiting eosinophils in the airways of asthmatics irrespective of the presence of an atopic status.