In this chapter we propose to deal with a group of psychiatric illnesses commonly described as the neuroses (sometimes referred to as the psychoneuroses). According to Henderson and Gillespie (1962), the ‘term neurosis has, from the standpoint of classification, two connotations. In the first and historical connotation, its meaning is purely descriptive. It is a term referring to conditions characterised by certain mental and physical symptoms and signs.’ They go on to say that the other connotation, from a medical standpoint, is more fundamental. ‘This is to the effect that the existence of a neurotic reaction is an indication of mental conflict.’ This latter aspect will be covered more fully from the medical angle by our colleague Dr Betts in a companion volume, entitled The Minor Psychiatric Disorders.