Effects of two well-known tranquillisers, reserpine and chlorpromazine on the reproduction ofP. viridis were investigated. There was a significant decrease on the ovarian index after reserpine (RSP) injection, whereas, chlorpromazine (CPZ) did not induce any change. But chlorpromazine has a profound effect on the testis index. Surprisingly, injection of the mixture ofRSP+CPZ induced a significant decrease in the ovarian and testis indices. Besides gonad index, the tranquillizer effect on histological profile of gonads was also studied.