A complex of two calcium binding proteins, MRP8 [also called cystic fibrosis (CF) antigen] and MRP14, proteins known to be expressed in cells of myeloid origin, has been shown to be present in higher amounts in the serum of CF patients and heterozygotes compared with normal subjects. We demonstrated here for the first time, by dot-blot analysis and immunocytochemistry, the expression and the presence of these S100 calcium binding proteins in the pancreatic cell lines CAPAN-1 and CFPAC-1, the latter provided from a patient with CF. Moreover, using immunocytochemical methods, we showed that the localization of MRP8 and MRP14 on the plasma membrane seems to be restricted to the cells expressing a cystic fibrosis transmembrane conductance regulator (CFTR) wild-type protein such as CAPAN-1 cells and CFPAC-1 cells transfected with a plasmid containing the nonmutated CFTR gene (CFPAC-PLJ-CFTR-6 cells). In CFPAC-1 cells, immunoreactivity remains in the cytoplasm throughout the stationary phase. We also showed an increased level of the mRNAs of the two proteins in the CFPAC-1 cells compared with those transfected with the nonmutated CFTR. The demonstration of a difference in the cellular localization of these two proteins and in their mRNA levels in the cell line of CF origin leads us to assume the existence of a possible correlation in the expression of the MRPs with that of the CFTR protein.