Improvements in the confinement, stability limits, current-drive efficiency and divertor performance, combined with steady-state operation, can lead to a more economical tokamak fusion reactor than one based on the present physics data base. The Tokamak Physics Experiment (TPX) is planned to extend the recent advances in these areas, achieved in pulsed tokamaks, to the steady-state regime. In so doing, it will develop a data base needed for the design of an economically attractive tokamak reactor.