Although phantom sensations and phantom pain are quite common sequelae of amputation and other related surgical procedures, these phenomena are not well understood. There are many, often conflicting theories which attempt to explain their nature and causes, and to provide a foundation for more effective treatment. This paper reviews recent literature on this topic. The review encompasses information about the prevalence and nature of phantom phenomena; evidence from empirical studies concerned with identification of possible predictors; and various psychological and neurophysiological theories that have been proposed in an attempt to explain why phantom sensations and pain are experienced. It is concluded that the fragmented approach adopted in the past has resulted in pockets of knowledge that are not too well integrated. There is therefore an outstanding need for a general theory to synthesise the knowledge gained to date about the multiplicity of factors associated with phantom phenomena. In this context, Melzack and Loeser's (1978) concept of "pattern generating mechanisms" may offer the most useful model for future research.