The study is recruiting people with cystic fibrosis (CF). The medical record is being extracted, and a blood sample is taken for DNA. The DNA samples are tested for variation both at the CFTR gene (the CF gene) and over the entire rest of the genome. Using large numbers of people with CF, and knowing who does and does not have CFRD, we identify genetic variations that associate with CFRD. Knowing these variations allows us to better understand the causes of CFRD, and with enough information, better to predict CFRD and identify people at particularly high or low risk of CFRD. People participating in this study also have the option to participate in related studies of other metabolic traits in CF such as over- and underweight.