Bronchial mucociliary clearance is analyzed in 13 clinically stable patients with chronic bronchitis in comparison with 7 normal non-smokers by measuring the rate of removal of inhaled monodispersed particles of resin (diameter: 8.1 .+-. 3.5 .mu.m) tagged with 99mTc. Particles delivered with a high insufflation rate are uniformly deposited on proximal airways. The pattern of distribution is comparable in all the subjects studied. In normal non-smokers, the percentage of bronchial radioactivity cleared 1 h after the inhalation was 34 .+-. 11.2%. The patients may be divided into 2 groups: Group 1 (n = 6) is characterized by a mucociliary clearance similar to the normals while group 2 (n = 7) shows a low mucociliary transport rate (decrease of bronchial radioactivity after 1 h < 10%).