The limitations imposed by the linearization of rate equations in chemically reacting flow problems using equilibrium reference states are discussed. A general linearized differential equation using nonequilibrium reference states is presented. An extended linear theory based on the general linearized equation is developed and shown to be effective for many type of reacting flows involving substantial variations of flow parameters brought about by finite rate chemistry. HEMICALLY nonequilibrium flow problems are of current importance in a number of applications ranging from gas dynamic lasers to rocket propulsion and re-entry aerodynamics. Because of the coupling between the finite rate chemistry and the dynamics of the flow, reacting flows with chemical nonequilibrium are considerably more difficult to treat than are corresponding flows of chemically inert gases. At the present, the majority of solutions of reacting flow problems are numerical and, as such, rely upon the availability of high-speed computers. The large number of flow parameter generally involved in reacting flow problems, moreover, have required very large amounts of computational efforts, even by modern computational standards, for the numerical solution of reacting flow