A model for the evolution of crystal shape is developed. The model accounts for faces growing in and growing out of an evolving crystal shape. The steady-state condition of the model determines the steady state crystal shape. The analysis is developed for a two-dimensional projection on the dominant face of facetted flat crystals. The effect of random seed shape on the steady-state shape is studied. (C) 2004 Elsevier B.V. All rights reserved.