The purpose of this study is to evaluate the safety and efficacy of gene therapy in cystic fibrosis using a recombinant adenovirus that is made replication deficient by deletions in the E1 and E3 regions. Recombinant adenovirus will be used to deliver an incremental dose of the human cystic fibrosis transmembrane conductance regulator cDNA to the upper and lower respiratory tracts of 15 cystic fibrosis patients.