Recent studies have suggested considerable particle retention in the bronchial ciliated airways 24 hours after depositing in the lung. A significant presence of particles in the ciliated airways at 24 hours post deposition may be indicated if beta-adrenergic treatment between 24 and 48 hours is shown to enhance particle clearance during this same period. The hypothesis was tested in ten young, normal subjects who inhaled Tc99m-iron oxide particles (5 micrometers MMAD) on three separate occasions. Following the first aerosol exposure, each subject inhaled a dose of albuterol sufficient to decrease specific airway resistance by 63% and clearance was measured by gamma camera over a 3 hour period. For the subsequent two aerosol exposures, baseline mucociliary clearance was measured, again over the initial 3 hour period, and then retention of particles was monitored with a six crystal gamma detector between 24 and 48 hours. During this 24-48 hour period, each subject inhaled 2 doses of either albuterol (a similar dose to that described above) or saline (double-blinded design). Albuterol significantly enhanced clearance at one hour post deposition.