For my master's dissertation project I traced the development of electrotherapy in eighteenth century Holland. Electricity’s medical value was by no means self-evident in the years following 1746, when the first Dutch patient was treated with it. Understandings of its effects on the body were still unclear, and judgements on the efficacy of electrotherapy varied. Nevertheless, by the end of the 1780s, a handful of authorities had emerged, who sought to define a coherent theory of medical electricity, identify a body of reliable case studies to undergird it, and a set of standard tools and procedures to put it into practice. Understanding how electrotherapy was transformed from a divisive miracle cure into a legitimate medical tool helps us understand how novel and entangled knowledge (like the science of electricity) is locally materialised (put into practice).