We investigated airway inflammatory cell dynamics during late asthmatic reactions (LAR) induced by toluene diisocyanate (TDI) in a guinea pig model developed by K. Tanaka et al. (Bull. Chest Dis. Res. Inst. Kyoto Univ. 1983: 16: 1-9). For sensitization, 10% TDI solution was applied once daily to the bilateral nasal mucosa of 41 guinea pigs for 7 consecutive days. One week after the sensitization, the animals were challenged with 5% TDI solution once a week. In addition, metyrapone (50 mg/kg) was injected intraperitoneally 24 h, and 30 min before the challenge, respectively. Airway tissue specimens (large bronchi and bronchioles) were obtained from the 41 guinea pigs at each time point (30 min, 3, 6, 24 and 168 h) after the challenge. Airway inflammatory cell dynamics were evaluated with regard to the onset and persistence of LAR. As a control, 7 guinea pigs were only exposed to ethyl acetate (a solvent for TDI) and sacrificed 6 h afterward. A histological examination of the airways revealed remarkable infiltration of eosinophils but failed to demonstrate infiltration of other inflammatory cells, including neutrophils, in the mucosal tissues of the bronchi and bronchioles during LAR at any time point (3, 6 and 24 h) after the challenge. Therefore, we conclude that eosinophils, but not neutrophils, play an important role in LAR in our model, a contrast to previous reports on human TDI-induced LAR in which neutrophils were also involved.