Particular instances of sexual deviation can not be discussed sensibly without first considering certain general issues.The first of these is the question of definition. The notion of what constitutes abnormal sexual behaviour has changed in the course of history and indeed its boundaries have expanded and contracted at different times. What emerges from the history of the concept is that it has been defined by the social and moral climate of the time and indeed sexual deviance can be seen, for the most part, as a social rather than a medical concept (Bancroft, 1974).