This study outlines the development and validation of a measure of reciprocity. The definition used to develop the measure extends traditional quid pro quo interpretations to include behavior designed to stabilize relationships in times of exchange breakdown. This includes resisting and not returning harm and making reparation for harm done. Reciprocity is positioned as an important interpersonal norm of stable marketing relationships given recent findings that relationships develop most strongly at the individual level. It is suggested that reciprocity leads to personal well-being; thus providing an additional motivation, over and above economic incentives, to develop and maintain relationships. Results of the scale development tests indicated a valid, two dimensional measure which correlated with key relational variables such as trust, commitment, satisfaction, self-esteem and reduced conflict.