This paper presents a general model for autocatalytic heterogeneous reactions in non-isothermal particles. We consider both quadratic and cubic autocatalysis and determine the effects of particle geometry, relative reaction rates, bulk fluid-phase composition, dimensionless temperature differences, and Arrhenius numbers on the catalyst effectiveness factor. In general, diffusion limitations within the heterogeneous phase can lead to effectiveness factors much greater than unity for both exothermic and endothermic autocatalytic reactions. Furthermore, multiple steady states can exist for exothermic reactions in a quadratic autocatalytic system, or for any reaction with a cubic autocatalytic system.