The proportional-integral (PI) control of continuously stirred tank reactors (CSTR) is addressed in this paper. The main ingredient in the formulation is the use of a novel PI control configuration derived from modeling error compensation ideas. The main theoretical contribution is a novel stability analysis of a wide class of CSTR. It is shown that the performance of an inverse dynamics feedback control can be recovered by classical PI control. This performance recovery includes the region of attraction and transient response.