My research concerns the history of collective investigation, a movement within late nineteenth-century medicine that promoted the production of medical knowledge through the collection of clinical facts. The practice of collective investigation involved the selection of a medical condition to investigate, the production of hundreds of uniform paper cards designed specifically to document the chosen condition, the circulation of these cards within a medical community, the collection of completed cards, and the publication of their contents. Collective investigation was first proposed in Britain in 1880 and was widely practiced in both Germany and the United States at state, national, and international levels. Though largely forgotten, I argue that collective investigation played an important role in the development of modern medicine, that the circulation of these uniform cards promoted the adoption of uniform clinical practices while simultaneously contributing to the consolidation of professional power.