||Patients with primary ciliary dyskinesia (PCD) have pronounced stasis of their respiratory secretions and therefore recurrent lower airway infections, which raises concerns for the development of lung function. Twenty four patients with PCD have been studied prospectively with a standardized regime in our clinic for 2-16 yrs with clinic visits, including spirometry 2-4 times per year, daily physiotherapy and monthly sputum cultures with subsequent specific antibiotic treatment. Lung function was significantly lower in the 12 PCD patients entering the cohort as adults when compared to the PCD patients entering as children (forced vital capacity (FVC) 70 versus 85% predicted; forced expiratory volume in one second (FEV1) 59 versus 72% pred). The lung damage did not relate to the type of ciliary dyskinesia. During the subsequent surveillance of the groups for a median of 14 and 7 yrs, respectively, the lung function remained stable in most patients. It is concluded that primary ciliary dyskinesia is accompanied by a progressive deterioration in lung function if undertreated, but lung function can be maintained with appropriate antibiotic treatment and regular physiotherapy. This emphasizes the need for early diagnosis of primary ciliary dyskinesia.