Abstract
The literature on parallel process from Searles (1955) to the present day is reviewed. It is noted that, despite the paucity of empirical evidence, the concept is widely used and has been discussed in relation to a wide variety of professional and client groups. Various explanations have been given for the phenomenon, which fall largely into two areas: identification and the adoption of reciprocal roles. It is suggested that there is value in viewing parallel process as both an interpersonal and an intrap-sychic phenomenon, and a new broader definition is proposed.