A coherent approach for the design of reactive crystallization systems is presented by incorporating reaction and crystallization kinetics, and mass transfer, into an existing equilibrium-based conceptual design method A generic model for a well-mixed crystallizer is developed; it is applicable to reacting systems with any number of components. The reaction, mass-transfer and dissolution Damkohler numbers, and the nucleation and growth numbers which result from the generic model represent the relative rates of the individual steps and their effect on the resulting crystal-size distribution and the crystallizer productivity is discussed. Estimates are provided for the typical values of the dimensionless numbers. To describe the solubility behavior of solid-liquid systems, a generalized equation for the isothermal solubility of a solute in the presence of an arbitrary number of other components is presented. The effects of the dimensionless numbers on the process paths are shown on the phase diagrams for systems involving up to four components. The utility of this integrated approach in the design of reactive crystallization systems is discussed using examples involving single and coprecipitation systems, and a salting out crystallization system.