In order to evaluate the degree of mast cell infiltration and determine their granulation state in the airways of patients with chronic bronchitis, bronchoscopy was performed in 25 chronic bronchitis subjects (10 smokers and 15 ex-smokers) with mucoid sputum production and in seven normal nonsmoking control subjects. Bronchoalveolar lavage and bronchial biopsies were examined using histochemical techniques. Subjects with chronic bronchitis had higher numbers of mast cells both in the epithelium (1.22 +/- 1 versus 0.22 +/- 0.2 mast cells per mm) and in the bronchial glands (137.4 +/- 37.9 versus 38 +/- 5.1 mast cells per mm2) than did control subjects (p < 0.01 and p < 0.001, respectively), whereas the numbers of mast cells in bronchoalveolar lavage (0.21 +/- 0.1 versus 0.18 +/- 0.1 mast cells percentage, nonsignificant [NS]) and in the lamina propria (87.5 +/- 66.4 versus 87.2 +/- 61.8 mast cells per mm2, NS) were similar in the two groups. In the smoking group of bronchitics an increase in mast cell numbers was observed in epithelium (1.6 +/- 1.3 versus 0.95 +/- 0.7 mast cells per mm, NS), in lamina propria (112.2 +/- 86.5 versus 71.7 +/- 45.7 mast cells per mm2), and in BAL (0.26 +/- 0.21 versus 0.16 +/- 0.17 mast cell percentage of total cells, NS) in comparison with the ex-smoker's group of bronchitics.(ABSTRACT TRUNCATED AT 250 WORDS)