PURPOSE OF THE REVIEW: Since cloning of the disease-causing gene 27 years ago, the development of cystic fibrosis (CF) gene therapy has been pursued. Here, we will summarize key findings with a particular focus on recent developments. RECENT FINDINGS: Almost 3 decades of research have highlighted the complexity of lung gene transfer and have generated a body of data that has recently led to the completion of a large phase IIB study. This trial has, for the first time, shown that nonviral gene transfer can, albeit modestly, stabilize lung function in CF and provides the impetus for further development of more potent gene transfer agents. Lentiviral vectors, specifically pseudotyped to enable entry into airway epithelial cells have most recently been developed. Persistent expression after a single dose and the ability to be administered repeatedly suggest that these viral vectors hold promise for the treatment of CF; a first-in-man clinical trial will shortly be initiated. SUMMARY: Although the development of CF gene therapy has been slower than initially anticipated, recent progress has been encouraging and has renewed the interest of academics and industry to pursue lung gene therapy.