Mucus volume in both central and peripheral airways was assessed in 13 patients, six with chronic bronchitis (CB) and seven with chronic pulmonary emphysema (CPE), by morphologic quantitative measurement in autopsied lungs, and the results were compared with those from four control lungs (NL). The patients with CB and CPE had severe obstructive impairment that did not differ significantly between the two groups (FEV1%, mean 45% in CB and mean 49% in CPE). Mucous hypersecretion during clinical remission differed significantly between the CB and CPE groups (mean 80 ml/day in CB and mean 8 ml/day in CPE). The length of the airway basement membrane and the area of mucus were measured with a digitizing computer. The volume ratio of mucus to airway lumen, which was defined as the volume ratio of mucus to airway lumen calculated as a cylinder by the length of basement membrane, was regarded as the mucus occupying ratio (MOR). MOR was significantly higher in CB lungs (4.1 +/- 1.0% in central airways and 19.6 +/- 3.8% in peripheral airways, mean +/- SE) than in NL (0.3 +/- 0.1% in central airways and 0.6 +/- 0.3% in peripheral airways, respectively) in both central and peripheral airways (p less than 0.05 and p less than 0.01, respectively), whereas no significant increase in MOR was found in CPE lungs, compared with NL. Furthermore, peripheral airway MOR was significantly higher than that of central airways in CB lungs (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)