Abstract. Wild-type and the F508 mutation of the cystic fibrosis transmembrane conductance regulator (F508-CFTR) were localised by confocal imaging in F508/F508 native airway epithelial cells using a well-characterised CFTR antibody. Surface nasal epithelial cells from three control and three CF individuals were obtained from nasal brushings. Cells were fixed, permeabilised and incubated with first antibody for 18h at 4C. Following labelling with second antibody, cells were viewed with the confocal microscope. Wild-type CFTR was localised predominantly apically, whereas F508-CFTR was located mainly inside the cell in a region close to the nucleus. Incubation of cells with MPB-07 (250M) at 37C for 2h resulted in pronounced movement of F508-CFTR to the cell periphery, but did not change the localisation of wild-type CFTR. The results show that F508-CFTR is mislocalised in native nasal epithelial cells and that its distribution is altered in response to the new CFTR activator, MPB-07. The findings should lead to development of a rational drug treatment for CF patients carrying the F508 mutation.