The aim of this paper is to emphasize the main aspects of the ways in whichdifferent pH levels influence the development of zebra fish (Danio rerio) embryos.During the experiments there have been used 6 variants with different pH levels inorder to monitor the development of zebra fish embryos in 40 ml Nunk culturedishes at optimum density (1 embryo/ 3 ml) and at an optimal temperature of28.5oC.It could be noticed that most embryos died in a pH=6 medium (70%). This meansthat such a medium is not suitable to embryo’s development. For the controlvariant (pH=7) it has been recorded the lowest mortality rate of only 23% and inthe case of other variants the mortality was of 30-40%.The studies of the pH influence upon the zebra fish embryo development haveunderlined the fact that little digressions from the optimal conditions can led toirreversible modifications within the roe which sometimes are even lethal.