To investigate the optimal lavage technique to study the airway response in patients with asthma, differential volume lavage was carried out in 22 normal subjects and 18 patients with red cedar asthma. Ten ml of fluid was instilled into a main-stem bronchus followed by 5, 10, 20, 50 and 100 ml into different segmental bronchi. Small volume lavage (less than 20 ml) in a main stem bronchus or a segmental bronchus recovered more epithelial cells and neutrophils while a lavage volume of 20-100 ml in a segmental bronchus recovered more lymphocytes, alveolar macrophages, albumin, IgG and alpha 1-antitrypsin. In patients with asthma, a higher proportion of epithelial cells was observed in the 20 ml segmental bronchus lavage 24 to 48 hours after bronchial challenge with plicatic acid, the chemical compound responsible for red cedar asthma. There was an increase in eosinophils and IgG with all volume lavages, but the changes were most marked in the 10 ml main bronchus lavage and the 10 and 20 ml segmental bronchus lavage. The results show the importance of using a systematic lavage protocol to characterize the cellular and protein changes in the airways of patients with asthma. A single volume lavage in one site may not encompass all the changes observed.