Optimal heat exchanger temperature profiles of exothermic tubular reactors were determined under the assumption of steady-state and plug-flow characteristics. The minimum principle of Pontryagin (optimal control theory) was applied in a straightforward analytical sense. To enable a trade-off between process performance and heat loss, a combined cost criterion was defined. In the first approach of specifying only, terminal costs, the optimal control input was of the bang-bang type that keeps the heat exchanger temperature constant at its maximum or minimum value. Afterwards, the terminal cost criterion was extended with an integral part that accounts for the global heat loss during the process. This integral cost part induced a control of the bang-singular-bang type. The desired performance call be met by selecting appropriate weights for terminal and integral costs.