A proto-oncogene, cellular myc (c-myc) gene, has been isolated from a tetraploid fish, goldfish Carassius auratus. The nucleotide sequence of 5021 base pairs covering the gene and its flanking regions was determined. The goldfish c-myc gene, probably like those of other animals, consists of two coding exons (exon 2 and exon 3) interrupted by an intron. Exon 2 and 3 together presumably encode a protein of 399 amino acid (aa) residues. The goldfish c-myc gene shares higher aa identities with those of the common carp (93.0% and 95.3%) and zebra fish (90.7%) than with those of rainbow trout (71.9%) or humans (56.0%).