In the burning fusion plasmas of next step devices such as ITER (2001 ITER-FEAT Outline Design Report IAEA/ITER EDA/DS/ 18 (Vienna: IAEA) p 2 1), the majority of the heating of the fusing fuel will come from the Plasma self-heating by fusion born a-particles. Recent advances in theoretical understanding, together with the development of new diagnostic techniques, make this a timely opportunity to survey the role of energetic particles in fusion plasmas and how it projects to future burning plasma devices.