In most populations, an appreciable fraction of cystic fibrosis transmembrane regulator (CFTR) gene mutations in patients affected by cystic fibrosis (CF) cannot be identified, and large gene rearrangements might be missed by standard analyses. We have searched large gene rearrangements in a sample of 25 North East Italian CF patients who, after an extensive gene analysis of 188 patients, still bear one or two unidentified CF mutations. A systematic gene screening by quantitative multiplex PCR of short fluorescent fragments was performed. Overall, 5/26 (19.2%) rearranged alleles were detected, bearing mutation 3120+1Kbdel8.6Kb (three patients), and c.4_IVS1+69del119bpins299bp (two patients). These mutations were observed in compound heterozygotes with F508del or termination mutations, and a pancreatic insufficient form of CF. These findings confirm the frequency of CFTR gene rearrangements recently observed in French CF patients.