A recent analysis of clinical data of patients aged 6–82 years collected in the cftr2 database and of their CFTR function revealed a moderate correlation between the forced expiratory volume in one second (FEV1) as a surrogate marker for the extent of lung disease and CFTR function determined by the CF genotype and calculated based on CFTR transport in rat thyroid and bronchial epithelial cells [5,40]. The gene discussed is CFTR; the disease is lung disorder.