Embryologic and larval developments of the fertilized gold fish (Carassius sp.) eggs were investigated in this research. Embryologic development of the fertilized eggs in the water of 24 °C and 7.1-7.4 pH obtained aquarium laboratory of the Fisheries Faculty, Istanbul University were completed at 73 hours. The new fertilized gold fish eggs, were found round, transparent colour and 1.4-1.6 mm diameter, the newly hatched larva were determined transparent and 4.3-4.4 mm in the measurements. During the first 2 hours perivitellin has been occured and after that 2.5 hours mytosis stage were conducted and morula stage was started in first 7 hours. In blastula stage (7.5 hours) periblast was beeing by blastoderm and gastrula stage was followed. Eyes vesiculles were occured in 21 hours, caudal sommits and pigmentation in 26 hours. Embrio was mooved in 70. hours and fry was hatched in 73 hours. Vittelus absorbed by the larvae in 76. hours and caudal fin was occured. Vitellus absorbtion was completted and swim blader was occured in larvae but nouth opening was not shown in 81. hours. Visceral organ and fins were shown and mouth oppening was appear in 82 hours. As a result, during the larval development period of gold fish environmental conditions were effect embryologic and larval development and breeding of the fish.