SUMMARY Twelve children with cystic fibrosis were admitted to a paediatric rehabilitation hospital for 17 days to take part in a training programme of vigorous physical excercise and sport. The daily inhalation-physiotherapy routine was stopped. Ventilatory status was assessed by spirometry and measurement of lung volumes one day before admission, one day after the end of the hospital stay, and 8 weeks later. Flow measurements of forced expiration had improved appreciably by the end of the course, but most of them returned to pretraining levels 8 weeks later. Lung volumes did not change significantly. Daily recordings of peak flow indicated improvement of airways function plus some ventilatory muscle training. Regular physical exercise could replace the inhalation-physiotherapy routine in some children with cystic fibrosis.Aerosol inhalation followed by chest physiotherapy is an essential part of the life-long therapeutic routine in cystic fibrosis (CF). Patient compliance however, is often poor, especially in older children.The efficacy of these procedures to mobilise and remove secretions seems to decrease with age. A more effective and popular alternative is needed.Swimming in conjunction with the inhalationphysiotherapy routine has been shown to increase sputum production and to improve ventilatory function.1 This stimulated us to study the changes in pulmonary function after inhalation and chest physiotherapy had been replaced by a short programme of intense physical exercise and sport. Patients and methodsSix boys and 6 girls, with a median age of 0I years (range 2 4/12 to 16 3/12) and a median clinical Shwachman score2 of 69 (range 37 to 86) were sent to a paediatric rehabilitation hospital situated in a mountainous area in upper Styria (altitude 1180 m above sea level). They were chosen from children attending the CF clinic at the University Children's Hospital, Graz, on the-basis of repeatedly positive sweat tests,3 a stable clinical condition, and willingness to participate.The routine therapeutic regimen of these children had included pancreatic enzyme replacement and appropriate diet. Chest physiotherapy administered by either a parent or the patient had followed aerosol inhalation twice daily. In addition 5 children were on oral antibiotics. None used bronchodilators. Five children had taken part in a previous study.' Two months before admission parents and children were instructed to keep strictly to the inhalationphysiotherapy routine.In order to reduce any seasonal or occupational influences on clinical condition or pulmonary function, the study was conducted in the summer holidays. The hospital stay lasted 17 days and during this time aerosol inhalation and chest physiotherapy were stopped.