The study followed the results of 0.85% CO2 influence on chick embryonic development. Biological material wascomposed of chicken eggs obtained from COBB500 hybrid broiler breeder parents. After weight determination ofchick embryos in different stages of development, egg components and embryos annexes, pH measurements ofalbumen and yolk sac were made. All of this analysis was made in order to determine the positive influence of 0.85%CO2 level on multistage chick incubation.