Non-linear internal model control (NIMC) of non-linear systems with input multiplicities is analyzed. The system is a continuous stirred tank reactor (CSTR) carrying out Van de Vusse reaction schemes and exhibiting input multiplicities in the manipulated variable (u) on the product yield (y). The system having two values of u to get a desired value pf y (one value of u has a positive gain and the other value of u has a negative gain) poses problem in the design of conventional PI controllers. Non-linear IMC designed based on the original state variable model equations drives the system input to a larger value rather than to a smaller value. Whereas the non-linear IMC designed based on a pseudo dynamic model equation drives the system input to either a larger value or to a lower value depending on the designer choice. The performance of the non-linear IMC is compared with that of the conventional PI controller.