During solidification, particles get pushed or engulfed by the freezing front. The interaction of the particles with the freezing front determine the final distribution of particles in the growing solid. In this paper, mechanisms and criteria for particle pushing are described. Problems with the classic theory on particle pushing are discussed. It is suggested that in most cases mechanisms based on fluid flow consideration are important for particle pushing in alloys that undergo shrinkage during solidification. A method for predicting particle redistribution during solidification using the criteria for particle pushing is suggested.