The development of any discipline is related to the strength of its underpinning theoretical base. Well-established disciplines have a diversity of clearly stated and competing theoretical frameworks to describe and explain theoretical constructs. Information systems (IS) is a relatively new discipline; many well-known IS theories (such as the technology acceptance model, theory of reasoned action and theory of planned behaviour) are borrowed from disciplines such as economics and psychology. This chapter outlines personal construct psychology, a psychological theory. Current applications of methodologies based in personal construct theory are discussed, and the positioning of the theory within a broader taxonomy of IS theory is explored.