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Complementary DNAs (cDNAs) encoding follicle-stimulating hormone (FSH)β, luteinizing hormone (LH)β and glycoprotein hormone (GPH) a subunits were isolated and characterized from ayu pituitary using a PCR technique. The FSHβ, LHβ and GPHα subunit cDNAs were found to be 556, 588 and 621 base pair (bp) long, encoding 384, 432 and 357bp long open reading frames, respectively. The deduced amino acid sequences of the putative mature forms of ayu GPHα and LHβ subunits were on average 63% homologous with those of other teleosts, whereas ayu FSHβ subunit was on average 42% homologous. These results show that ayu has two different types of gonadotropins (FSH and LH), as in other teleosts. FSHβ subunit mRNA was mainly detected during early vitellogenesis and spermatogenesis. In contrast, LHβ subunit mRNA was detected during the late phase of gonadal development, suggesting that the primary function of FSH may be to initiate gametogenesis, while LH may have a role in the development of gametes.