Good quality clinical trials are essential to inform the best cystic fibrosis (CF) management and care, by determining and comparing the effectiveness of new and existing therapies and drug delivery systems. The formal inclusion of quality of life (QoL) as an outcome measure in CF clinical trials is becoming more common. Both an appropriate QoL measure and sound methodology are required in order to draw valid inferences about treatments and QoL. A review was undertaken of randomised controlled trials in cystic fibrosis where QoL was measured. EMBASE, MEDLINE and ISI Web of Science were searched to locate all full papers in the English language reporting randomised controlled trials in cystic fibrosis, published between January 1991 and December 2004. All Cochrane reviews published before December 2004 were hand searched. Papers were included if the authors had reported that they had measured QoL or well being in the trial. 16 trials were identified. The interventions investigated were: antibiotics (4); home versus hospital administration of antibiotics (1); steroids (1); mucolytic therapies (6); exercise (3) and pancreatic enzymes (1). Not one trial evaluated in this review provided conclusive results concerning QoL. This review highlights many of the pitfalls of QoL measurement in CF clinical trials and provides constructive information concerning the design and reporting of trials measuring QoL.