Transferrin is a monomeric iron-binding glycoprotein. To investigate the structure of the transferrin gene in teleosts, we prepared a genomic DNA library from the medaka (Oryzias latipes). The medaka transferrin gene was isolated, and its nucleotide sequence was determined. The full length of this gene is approximately 8.5 kb, and it is organized into 17 exons separated by 16 introns. The exons are similar in size to those in the genes for human transferrin, chicken ovotransferrin, and mouse and bovine lactoferrin. However, the introns are smaller than those previously reported in the transferrin family of genes. The 5'-flanking region of the medaka transferrin gene contains an estrogen-responsive element, glucocorticoid-responsive elements, an iron-responsive element, metal-responsive elements, and Spl binding sites. The transcription start point is located 35 bp upstream of the start codon.