Because of the time and the emotional cost involved in performing daily conventional chest physiotherapy in patients with cystic fibrosis, a 3-year prospective study was undertaken to compare the long-term effects of postural drainage accompanied by percussion and the forced expiratory technique with the effects of the forced expiratory technique alone. Patients who performed the forced expiratory technique alone had mean annual rates of decline that were significantly different from zero for forced expiratory volume in 1 second (p less than 0.001), forced expiratory flow between 25% and 75% of vital capacity (p less than 0.001), and Shwachman clinical score (p less than 0.004). In the group performing conventional physiotherapy with percussion and postural drainage, only the mean annual rate of decline for forced expiratory flow between 25% and 75% of vital capacity was significantly different from zero (p less than 0.03), and it was significantly different from the mean rate of decline associated with the forces expiratory technique alone (p less than 0.04). We conclude that conventional chest physiotherapy should remain a standard component of therapy in cystic fibrosis.