Recently, IS researchers have borrowed theories from other academic fields in the hope of enriching their theorising about the use, adoption and diffusion of material systems by human actors. Situated Action, Structuration theory and Actor-Network Theory (ANT) are cases in point. Arguably, rather than borrowing theories ready-made from alien disciplines, we should investigate their meta-theoretical commitments and apply these directly to IS problems. This paper argues that the notion of viewing intentional action from the “ground view” of a situated agent is the essential theoretical move underlying these theories. The notion of situated action is developed systemically as an alternative to the widespread deliberative view of action, and it is shown that the key notions of Structuration and ANT arise out of this exposition in a rather natural way. By demystifying these theories in this way, it is hoped that in future IS researchers might draw directly on the more fundamental notion of situated action in theorising the role of IT/IS in human intentional action.