Abstract: Stable austenite cell structure in high manganese casting steel was obtained by strictly controlled directional solidification technique. The experimental results have shown that when cerium content increases the cell structure changes into dendrites and then into separated crystals.The influence of cerium on manganese segregation in cells, in columnar crystals and dendrites was studied by ele-ctronprobe analysis. on the basis of some previous work of other authors and with the consideration of solute diffusion in solid state, a formula which describes manganese distribution in high manganese steel was derived. By analysis of the experimental data, it has been shown that the solute equilibrium partition coefficient Ko is the determinative factor which influences dendritic segregation.