A model for the prediction of faceted crystal shape evolution during growth or dissolution is presented. An ab initio mechanistic model for the relative growth or dissolution rates is also described for organic molecular crystal systems. The shape evolution model proves that while growing crystals evolve toward a steady-state shape, dissolving crystals evolve away from a steady-state shape. Thus, crystals cannot achieve a steady-state during dissolution. This methodology may be used to probe crystal shapes that are obtainable by growing and/or dissolving crystals, including pharmaceutical crystals, inorganic materials and geological minerals. The technique has been successfully applied to predict the shape evolution of succinic acid growing or dissolving in water. (c) 2007 American Institute of Chemical Engineers.