NGAL, a protein recently isolated from human neutrophils, is a novel member of the lipocalins. NGAL binds a derivative of the bacterial chemotactic peptide formylmethionyl-leucyl-phenylalanine and may have important immunomodulatory functions. We here report the cloning of a cDNA for NGAL covering a 63 bp 5' untranslated region and the coding region of 591 bp. The cDNA encodes a protein of 197 amino acids, with a 19 amino acid leader sequence and a mature protein of 178 amino acids. Alignment of the cDNA sequence of NGAL to the rat analogue, alpha 2-microglobulin related protein, demonstrates a very high degree of conservation of this lipocalin. Northern blotting of a variety of tissues revealed that NGAL is mainly expressed in myeloid cells, where a signal of approximately 850 bp is observed. A faint signal was observed in fetal and adult human lung tissue. The molecular cloning of the NGAL cDNA allowed the recombinant production of NGAL in E. coli.