CF is an inherited life-limiting, disorder which although can affect a number of other organs, mortality results primarily from progression of lung disease. Acute deteriorations in lung infection, termed 'acute pulmonary exacerbations' (APEs) are the single most important cause of CF morbidity and mortality. Despite this, little is understood about the pathophysiological processes that trigger APEs, but are thought to be driven by respiratory infections. However, there is no substantive evidence to date that the presence or load of individual species is driving this process. This may reflect the complex underlying microbial diversity found in the CF lung at both the inter and intra species level. Metagenomics will be carried out on daily sputum samples collected from CF patients in order to characterise longitudinal patterns of the within-host diversity of bacteria within the CF lung, and how these changes relate to clinical events. This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/