‘Relationship is the soul of casework’ says Fr Biestek at the beginning of his book on the Casework Relationship. The forming of relationships between persons is one of the basic necessities of life, for man was made a social being. Relationship comes into every sort of personal and social situation. Nevertheless, the use of relationship in a particular way and for a particular purpose is the essential and basic factor in social work. It is, as Fr Biestek says, the ‘soul’ of casework and without it social work would be lifeless and meaningless. The theory of relationship in social work has been analysed by some of the ablest thinkers in the social work field. My aim in this paper is not to recapitulate what is in the text books or to attempt to summarise the literature about relationship. To do this would be both boring and ineffective.