This paper reviews recent developments in the analysis and calculation of multiphase equilibria involving chemical reactions. Emphasis is placed on the reaction tangent plane and its importance for stability analysis. Calculation methods to locate the global minimum of the Gibbs free energy are reviewed with emphasis on the GOP method that achieves epsilon-global convergence. Methods for the simulation and design of reactive-distillation columns are considered with emphasis on reactive azeotropes and reactive residue curves for chemical reactions at equilibrium or kinetically controlled.