The effect of extracted peptide factor with bradykinin potentiating activity from venom of Buthus occitanus on oocyte maturation and spermiation were studied in adult female and male Gambusia affinis holbrookii fish during the resting stage. Twenty four hours after the injection of a single sublethal dose (1 ug/g) of this extracted factor, the degenerating ovocytes in the female fish were completely absent, the number and size of the young ovocytes were increased and mature ovocytes were observed in the treated fish but none in the control fish. In adult male Gambusia, the injection of this factor caused a decrease in the number of immature spermatophores to produce a significant increase in the number of mature ones. This biological effect was basically interpreted to the direct initiating mechanism of such a venom factor or endogenously activated bradykinin in these organs or indirect effect through the activation of prostaglandin synthesis.