Here, we demonstrate the presence of multiple isoforms of palate lung nasal epithelial clone (PLUNC) in human nasal lavage fluid (NLF). Eight isoforms were separated by two-dimensional gel electrophoresis (2-DE), and peptide mapping of the proteins was performed using MALDI-TOF MS (matrix assisted laser desorption/ionization time of flight mass spectrometry) of tryptic and asparginase cleavages. The identification was verified by amino acid sequencing after analysis of collision-induced dissociation (CID) fragmentation spectra with nanoelectrospray MS/MS. One isoform showed an electrophoretic mobility shift after N-glycosidase treatment, indicating that at least one of the PLUNC isoforms is glycosylated. We also demonstrate that PLUNC in NLF binds to lipopolysaccharide (LPS) in vitro; indeed, out of all proteins present in NLF only the PLUNC isoforms were found to adsorb to an LPS-coated surface. These results show that PLUNC is expressed as multiple LPS-binding isoforms in human NLF. The possibility that PLUNC may play a role in the innate immune response of the upper airways is inferred.