An algorithm to design simple gain scheduled nonlinear PID controllers for nonlinear plants is investigated. Design information is obtained from measurements of the nonlinear plant about selected equilibrium points. Simulations are performed on two different nonlinear CSTR models. The first simulation produced an unexpected result: that linear output feedback performed better than state feedback for the particular model. The second simulation showed that the nonlinear PID controller performed as well as a complex nonlinear controller. A literature search for similar nonlinear controllers concluded that the nonlinear PID controller presented in this thesis did not provide a unified framework for previous work. / Master of Science