A partial genomic library of sea bass DNA was constructed and screened with a goldfish NPY cDNA probe. Two identical clones were isolated and sequenced. The clones contain a segment with high identity to exon 2 of the NPY gene in tetrapods. This segment encodes a 62-amino acid peptide consisting of a signal peptide of 28 amino acids and the main portion of the mature NPY (34 amino acids). In the latter extension, sea bass NPY shows high identity with the human and deduced ancestral gnathostome sequences (88 and 91%, respectively). The open reading frame is followed by a consensus splice donor site. Northern blot hybridization to examine tissue distribution detected a 1-kb RNA transcript restricted to brain tissue. These data show that the NPY gene of this teleost fish has the same intron positions as tetrapods for at least two of the gene's three introns. In addition, the high evolutionary conservation of NPY is corroborated since sea bass NPY exhibits the same identity to both goldfish and human NPY.