The aim of this study was to elucidate the mechanism of the formation of the widespread mucous-plugging observed in autopsied lungs from patients with bronchial asthma. We performed morphometric analysis of airways of autopsied lungs from eight patients with bronchial asthma (Group BA), and compared it with those of six chronic bronchitics (Group CB) and four control patients (Control). The following parameters were measured in paraffin sections: volume proportion of bronchial glands to bronchial wall (Gland%); goblet cell granules to total epithelial layer (Goblet %); intraluminal mucus expressed as the mucus occupying ratio (MOR); volume ratio of intraluminal mucus continuous with goblet cells to total intraluminal mucus (Vc/Vtol %); and surface ratio of the contact surface of intraluminal mucus continuous with goblet cells to the total luminal surface (Sc/Stot %). Gland%, Goblet %, and MOR or inflammatory cell numbers in the airway walls both from Group BA and CB were larger than those from the Control group. However, no significant differences were observed between Group BA and CB in Gland%, Goblet %, MOR or inflammatory cell numbers, except for the eosinophil number: i.e. 23 +/- 3, 22 +/- 3 and 6 +/- 2% in Gland%; 22 +/- 9, 5 +/- 4 and 2 +/- 2% in Goblet%; 10 +/- 3, 18 +/- 3 and 0.3 +/- 0.5% in MOR; 199 +/- 68, 10 +/- 3 and 2 +/- 2 cells. mm-2 in eosinophil number of the peripheral airways from Groups BA, CB and Control, respectively. In contrast, marked and significant increases were observed both in Vc/Vtot% and Sc/Stot% in Group BA compared to Groups CB and Control both in central and peripheral airways: i.e. Vc/Vtot% in the peripheral airways was 53 +/- 5, 4 +/- 3 and 0.8 +/- 0.8% from Groups BA, CB and Control, respectively (BA vs CB or BA vs Control, p < 0.01 each). These findings suggest that the continuity of goblet cells and intraluminal mucus or lack of full release of mucus, from goblet cells, is peculiar to asthmatic airways, and may contribute to the formation of mucous-plugs.