Many variables have been proposed as additions to the theory of planned behaviour structure, and evidence exists to support the value of a measure of ethical obligation and self-identity. Furthermore, some research has suggested that ethical obligation may serve as an antecedent to attitude as well as intention. This paper presents findings from a large scale survey that highlights the usefulness of ethical obligation and self-identity in the prediction of intention. Additionally, the role of both these variables in the prediction of attitude is also suggested. This is examined within the ‘ethical’ context of fair trade grocery purchases. Methodological implications for further research are discussed.