Pseudomonas aeruginosa plays a crucial role in the lung pathology of cystic fibrosis (CF). We showed that acute infection with P. aeruginosa has a substantial impact on gene transfer into lung epithelial cells mediated by polyplexes. As an extension of those studies we report here on the effect of chronic pulmonary infection with P. aeruginosa on transfection of lung epithelial cells by viral and nonviral vectors. As an in vivo model of the persistent chronic infection in patients with CF we used C57BL/6 mice intratracheally infected with P. aeruginosa encapsulated in agar beads. Two weeks after infection the presence of viable bacteria in the lungs was confirmed, mostly in the bronchial lumen. In lung tissue sections stained with hematoxylin and eosin, extensive inflammatory infiltrations were found. At that time point the mice received an intratracheal dose of luciferase gene complexed with either Lipofectamine (Lf), a GL67 lipid mixture (GL67), or polyethylenimine (PEI) or with lentivirus (LV) as a carrier system. Luciferase activity was determined by a luminescence assay in supernatants of lung homogenates. The transfection level induced by PEI/DNA polyplexes complexed with serum albumin was decreased in infected mice. Lf-mediated transfection was almost completely blocked in infected mice. Transfection levels in mice treated with LV or plain PEI/DNA polyplexes were unchanged in infected animals as compared with control mice. The only carrier that displayed a clearly increased transfection level in infected mice was the GL67 lipid mixture, which is tentatively ascribed to the presence of polyethylene glycol in this carrier.