The aim of this study was to establish reference values for mucociliary clearance and mucociliary clearance reserve capacity as determined by beta 2-adrenergic agonist-induced increase in mucociliary clearance. We studied 62 healthy females (n = 33) and males (n = 29). Their ages ranged evenly between 18 and 84 years. Fifty-three of the subjects were life-long non-smokers, while nine were ex-smokers. Multiple linear regression analyses showed that mucociliary clearance was significantly faster when the radioaerosol was deposited in the central airways than when it was deposited in the peripheral airways, and faster in life-long non-smokers than in ex-smokers. There was no influence of age, and no convincing association with sex. The variation was less within than between subjects. Mean mucociliary clearance reserve capacity was 21.3% (SD: 10.0%, P < 0.0001). The beta 2 agonist-induced increase in lung mucociliary clearance was significantly larger (P < 0.05) than the stimulation which has previously been reported in patients with asthma, bronchiectasis or cystic fibrosis. The signal-to-noise ratio of the mucociliary clearance reserve capacity in relation to measurement of baseline mucociliary clearance indicates that measurement of mucociliary clearance reserve capacity may be a more efficient means of distinguishing between "normal" and "abnormal" mucociliary clearance than single measurement of baseline mucociliary clearance.