The testes and ovarian development and maturation were achieved by combinative injection of carp pituitary extraction( CPE) and human chorionic gonadotropin ( HCG) for 5- 6 times in male and 9- 10 times in female Japanese eel ( Anguilla japonica ) . The mGnRH contents in the telencephalon, disencephalon, mesencephalon and hypothalamus signif icant ly increased after injection of CPE + HCG in male and female Japanese eel, but contents in the metencephalon and myelencephalon did not change. Injection of CPE HCG also increased the cGnRH- ò contents in the metencephalon and myelencephalon in male Japanese eel, but had no effect in the female. The serum GtH levels in male and female Japanese eel increased dramatically 1 day after each injection of CPE HCG, then gradually decreased 10 days after. However the serum GtH levels in female Japanese eel remained significantly higher than the corresponding control in 10 days after 7 inject ions. The serum testosterone concentration increased after injection of CPE HCG and kept on a high level in female Japanese eel, but did not change during the time of 1- 4 injection in male Japanese eel. The serum 17B- estradiol contents were not dif ferent with the corresponding controls during 4- 6 injections in female Japanese eel, but increased after 7 injections.