We investigated, in a double blind fashion, the acute effect of an inhaled beta 2-agonist drug (salbutamol) on mucociliary clearance in 20 patients with chronic bronchitis: ten treated with the drug and the remaining ten with placebo. Following inhalation of pre-sized human albumin microspheres with a mass median diameter of 1.5 micrometers, radioactivity was recorded for one hour (control period) with the patient in the supine posture with a large field computerized gamma camera collimated over the chest. At the end of the first hour, without moving the patient, either salbutamol (500 micrograms) or placebo was nebulized from a commercial canister and recording carried out for another two hours. At the end of the recording period areas of interest were selected and time activity curves generated, from which the percentage activity cleared in the first, second and third hour was calculated. Whereas no significant differences in clearance between the two groups were found in the control period, inhaled salbutamol significantly increased mucociliary clearance rate; particle removal in the second hour (test period) was 36.42 +/- 5.61 (SD) percent for the group treated with salbutamol, and 10.87 +/- 2.47 (SD) percent for the group receiving placebo.