Cystic fibrosis affects around 10,000 people in the UK and an estimated > 100,000 worldwide. It is a multisystem condition, with lung disease being the most significant, leading to early infection, inflammation and scarring. Currently, despite huge improvements in clinical care, the median age of death in the UK is just over 30 years. Babies are now diagnosed on newborn screening and are usually asymptomatic, but lung disease begins early. Disease progression is variable and influenced by a number of factors, one of the most important being the frequency of pulmonary exacerbations (PEx), poorly understood periods of increasing symptoms and a fall in lung function; with a quarter of patients experiencing a PEx having permanent loss of lung function as a result. Currently, PEx are detected once fully established; earlier detection, perhaps by monitoring for warning signs in the community, could lead to earlier treatment and improved outcomes. We will aim to recruit all paediatric patients at the Royal Brompton Hospital to look in-depth at their specific characteristics and to look for potential biomarkers in samples collected at home or in clinic to identify a PEx before it's established. A subset will fill in either a web based symptom diary or be given home monitoring equipment and carry out home sample collection over 6 months as part of a multi-centre study. The children will be separated into age bands for analysis (0-2 yrs, 3-5 yrs, 6-11 yrs, 12-17 yrs inclusive) in order to correct for the potentially more risky period of adolescence. The aim of this study is to test the feasibility of home monitoring and sample collection at home or in clinic to identify these PEx without adversely affecting quality of life. We aim to identify the most at risk patients in each age group in order to direct potential interventions.