Abstract: The purpose of this investigation is to examine the feasibility of using ultraviolet irradiation for producing gynogenetic diploid goldfish (Carassius auratus) and to look for the naturally gynogenetic population of crucian carp (Carassius auratus gibelia) in our country.The eggs of goldfish inseminated with irradiated milt of grass carp (Ctenopharyngodon idellus) or Hua-nan carp (Cyprinus carpio rubrofuscus) began with a haploid gynogenetic development. All haploid embryos, however, were abnormal in development and died before hatching. If goldfish eggs were held for 2 minutes in water of 18°—19℃ after addition of irradiated milt, followed by exposure to 0°—3℃ water(with crushed ice) for 20 minutes and then incubated at room temperature, we could obtain 4.5—11.9% (average 7.4%) viable diploid fry.The results of embryonic examination of thirty eight crucian carp (among them thirty three were caught from Shuangfeng reservoir in Fangeheng County. Heilong-jiang Province) proved that all of them reproduced by natural gynogenesis.Finally, the teratogenic effect of irradiated spermatozoon on gynogenetic haploid embryos is discussed.