Drug Name: Dry powder mannitol for inhalation Phase: 2 Indication: Paediatric and adolescent cystic fibrosis Trial Centres: Multicentre Sponsor: Pharmaxis Limited, 20 Rodborough Road, Frenchs Forest, NSW 2086 Australia Trial Duration: 27 weeks Number of Subjects: 160 Trial Design: Randomised, multicentre, double-blind, placebo-controlled, crossover Primary Objective: To determine the effect of eight weeks of twice-daily treatment with inhaled dry powder mannitol on lung function (FEV1) in subjects with CF who are aged six to seventeen years Dosage and Administration: Trial drug is to be administered via a dry powder inhaler.