Formulation and delivery of plasmid DNA–liposome complexes have been refined in a large series of preclinical studies,4, 5 and safety,6, 7 molecular efficacy, and practical doses have been assessed in several phase 1 and 2a studies in patients with cystic fibrosis.1, 3 We did this study to assess the clinical efficacy of the non-viral CFTR gene–liposome complex pGM169/GL67A8 after repeated delivery to the airways. This evidence concerns the gene CFTR and cystic fibrosis.