It is very important to develop efficient and stable techniques for obtaining fertilized eggs with good quality as well as sufficient quantity, particularly for difficult species as Japanese Sea Bass. Effects of a single hormone or combined hormone treatments on induction of oocyte maturation and ovulation were examined in wild Japanese Sea Bass which were collected by longlines near the coast of Kujukuri in Chiba Prefecture during spawning season in 1989 and 1990. The present data were evaluated by comparison with previous data obtained from 1982 through 1988. HCG (human chorionic gonadotropin) from 1982-1990, SP (silver carp pituitary extract) in 1989 and CP (chum salmon pituitary extract) in 1990 were used in the respective experiments. HCG-SP group produced viable eggs by artificial insemination. Spontaneous spawning in tanks was induced by HCG-SP and SP treatments, but the number of eggs was evidently larger in HCG-SP group. HCG-CP treatment was more effective than HCG-SP treatment in 1989. The number of floating viable eggs and hatched larvae induced by the combined hormone (HCG and pituitary extracts) treatment appeared to be greater than those obtained by a single hormone treatment conducted from 1982 through 1988. These results suggest that the combined hormone treatment is effective in inducing ovulation for Japanese Sea Bass.