The engine described in this paper has the following features and potential improvements over conventional gasoline or Diesel engines: 1. Much higher thermal efficiency, 2. Lower emissions, 3. Less stringent fuel requirements, 4. No ignition system required for steady operation, 5. Highly efficient operation at low compression ratios, 6. High power to displacement ratio, 7. Similar to conventional engine hardware. In this paper the thermodynamic advantages of regeneration with Otto and Diesel cycle engines are presented, along with a brief description of past attempts to provide regeneration in a reciprocating internal combustion engine. Finally, the single cylinder regenerated internal combustion engine concept is presented and described, along with its inherent and potential features, advantages, challenges, and issues.While the thermodynamic validity and advantages of regeneration are straightforward and well founded, past attempts to exploit regeneration in reciprocating engines have not been sufficiently promising to merit further development. The engine design concept presented here offers promise as a means to attain the high potential and payoff of regeneration in a reciprocating internal combustion engine.