Detailed pulmonary function tests were performed on 12 patients with cystic fibrosis (CF) before and after 3 days treatment with postural drainage incorporating the forced expiration technique. The results following treatment showed a statistically significant improvement in FEV1 (P less than 0.001), FVC (P less than 0.001), PEFR(P less than 0.001), PIFR (P less than 0.001), and VEmax50 (P less than 0.025). The study demonstrates objective benefit from this form of physiotherapy in cystic fibrosis patients with copious bronchial secretions.