A nonlinear controller design for a packed-bed reactor is presented. The scheme employs a two-tier approach in which, first, a low-order nonlinear model is developed and, subsequently, a feedback linearizing control law is synthesized. The reduced-order model treats transport mechanisms in the reactor as a nonlinear wave which propagates through the bed. Application of input-output "linearizing" control yields linear dynamics over a wide range of operating conditions. The practical issues of implementing the resultant digital, implicit, nonlinear control law on an actual system are addressed. Closed-loop simulations are used to illustrate the robustness properties of the nonlinear controller. In addition, the relative strengths of this approach over traditional linear control are identified.