Of the more than 50 members of the ABC-transporter family, MRP1 (ABCC1) has been identified to have the highest protein expression levels in human lung tissues. The subcellular localisation and functional activity of the transporter in lung epithelia, however, remains less well investigated. The aim of this project was to study MRP1 expression and function in human respiratory epithelium using the NCI-H441 cell line as well as freshly isolated human alveolar epithelial type (AT) II and type I-like cells in primary culture in vitro. ABCC1 gene expression was comparable between ATII and ATI-like cells, while MRP1 protein expression was higher in ATI-like cells from three different patients, when compared to ATII cells. Gene and protein expression remained stable over thirty passages of NCI-H441 cells studied, independent of culture conditions. Surface biotinylation confirmed basolateral expression of the transporter in NCI-H441 cells. Efflux experiments found the transporter to be functionally active and sensitive to specific inhibitors in both, NCI-H441 and primary cells. Bi-directional transport experiments revealed a net absorptive, MK-571 and telmisartan-sensitive CF flux, underlining the basolateral localisation of the transporter. This study shows that the cell line NCI-H441 is a useful in vitro tool for the investigation of MRP1 function in distal lung epithelium.