Abstract: The method of in vitro ovulation of the ovarian fragments of the toad,Bufobufo gargarizans,in a medium containing carp pituitary suspension has been emp-loyed to assess the gonadotropic activity of carp pituitaries collected from the samelocality but in different months of the year.Results of our experimentation indicatethat carp pituitaries collected from February through March have the strongest gona-dotropic effect,while those collected in December the weakest.Potency of the glanddecreases gradually from March onwards,and increases gradually after Decemberuntil a maximum is reached in February;thus carp pituitaries exhibit a definitecyclic change in the relative amount of the gonadotropin they contain.This findingimplies that in central China,early spring is the best season for collecting carppituitaries for the use of induced spawning.