Background: Segmental allergen challenge is a powerful tool to study inflammatory reactions in asthmatic airways. There is little information on the early events at 5 min and 4 h after allergen challenge with respect to the cell influx and the chemokine interleukin–8 (IL–8). Methods: Seven mild to moderate allergic asthmatics (AA group), 5 allergic nonasthmatics (ANA group) and 5 nonallergic controls underwent segmental allergen challenge, with allergen doses based upon skin reactivity. Bronchoalveolar lavage (BAL) samples were obtained before, 5 min and 4 h postchallenge, and were analyzed for cell numbers and differential counts, eosinophil and neutrophil chemotactic activity, and levels of IL–8. Results: At 5 min postchallenge, no changes were observed compared to baseline. At 4 h postchallenge, an increase was found in the number of neutrophils and the levels of IL–8, which was dependent on the dose of allergen in the AA and ANA group. At the same allergen dose, the increases in neutrophils and levels of IL–8 were calculated to be 91 and 67 times higher, respectively, in AA than in ANA. Levels of IL–8 correlated with the number of neutrophils and with the in vitro neutrophil chemotactic activities in BAL fluid. Conclusions: Neutrophil chemotactic activity is increased in BAL fluid at 4 h after segmental allergen challenge. We suggest that apart from IgE–mediated mast cell degranulation, additional local factors in the airways determine the degree of IL–8 increase and neutrophil influx.