Simplification of the computations necessary for the stability analysis of a nonlinear spatially dependent reactor has been achieved for the semigroup method by means of the generalized mean value theorem and a generalization of a classical stability result. Conditions sufficient for asymptotic stability are derived. A simple numerical example and a comparison of this method with previously proven methods indicate that smaller domains of allowable perturbations result, but that the calculational procedure is simplified in that the nonlinear equilibrium problem does not have to be solved.