This paper assesses the strengths and weaknesses of medium theory as a model. In surveying the critical reception of medium theory, the paper re-evaluates the charge of technological determinism that has been brought against this theoretical model. Alternative models incorporating technologies and social systems, such as Actor Network Theory, are considered, but the paper affirms the emphasis in medium theory on the intrinsic properties of media technologies. The paper points to the tacit influence of medium theory in everyday claims made for new media technologies and their transforming capacity. As a result of a reconsideration of medium theory, the paper proposes a theoretical approach sensitive both to the social context of media technologies and to the properties of those technologies themselves.