It is quite a challenge to summarise reversal theory, an innovative theory of motivation, emotion and personality, in a single chapter. Michael Apter’s two books outlining the theory (Apter, 1982, 1989) contained 369 and 195 pages of explanatory text, respectively. This chapter will, however, take on this challenge in order to provide readers with a basic knowledge of reversal theory. Applications of the theory to counselling athletes will be developed in later chapters. Figure 1.1 shows the concepts from reversal theory that are most relevant to athlete counselling.