Direct quantitative comparisons of the dynamic controllability of four alternative tubular reactor systems are given in this paper. An exothermic, irreversible gas-phase reaction, A + B --> C, is carried out in a packed-bed tubular reactor in a process that includes reaction, separation, feed preheating, and gas recycle. The four alternative tubular reactor designs are (1) a single-stage adiabatic reactor, (2) multistage adiabatic reactors with interstage cooling, (3) multistage adiabatic reactors with cold-shot cooling, and (4) a single-stage cooled reactor. All of the adiabatic systems are open-loop unstable (exhibit limit-cycle behavior) because of the sensitivity of the first reactor, which propagates thermal waves through the system. The cooled reactor system is open-loop stable for base-case parameters. The single-stage adiabatic reactor and the multistage adiabatic reactor system with intermediate cooling are closed-loop stable. However, the optimal seven-bed multistage adiabatic reactor system with cold-shot cooling is closed-loop unstable because of the severe disturbances generated by manipulating cold-shot flows. If the number of beds is reduced to three, the system is closed-loop stable. The cooled reactor is the most controllable.