The aim of our study was i) to establish typical VTE values, in the FVB and B6;129 backgrounds, for F508del-CFTR and cftr-/- mice, respectively, ii) to determine the repeatability of VTE measurements, iii) to determine threshold VTE values distinguishing between the CF and WT electrophysiological responses in F508del-CFTR mice. The gene discussed is CFTR; the disease is cystic fibrosis.