A new general theory of motivation and personality known as "reversal theory" (Apter, 1982) 'is introduced. It is argued that this theory, although deriving from the work of Western psychologists, shares a number of features which have come to characterise much of modern Soviet psychology, including use of the concept of "activity" in exploring both mental and behavioral processes. Some of the main concepts of the theory are outlined, especially the notions of bistability (which is contrasted with homeostasis), metamotivation and metamotivational reversal, the telic and paratelic systems, and metamotivational dominance. The empirical research generated by reversal theory is briefly reviewed, as well as some of its implications for practice.