ABSTRACT CAREFUL AND COMPLETE OBSERVATION OF THE PATIENT;” NURSES AND THE SOCIOTECHNICAL SYSTEM OF MEDICAL RESEARCH, 1930-1962 Amanda L. Mahoney, MS, RN Julie A. Fairman, PhD, RN, FAAN This study addresses the history of nurses working in medical research between 1930 and 1962, a time of tremendous growth in the use of experimentation to further clinical knowledge. Nurses were part of an intricate network of people, machines, knowledge and space—a socio-technical system—that made the clinical discoveries of the mid-20th century possible. Nurses were heavily involved in the day to day practices of medical research, thus this dissertation employs a microhistory approach, focusing on individual research projects conducted at the Hospital of the University of Pennsylvania (HUP) in Philadelphia, Pennsylvania. Archival sources related to clinical trials and nursing at HUP were examined as well as the historical records of funding agencies. Nurses performed important, skilled tasks including data collection and complex patient care. The requirements of research studies as well as the new technologies associated with clinical trials required nurses to develop methods and systems to accommodate an increased work load, collect data, and implement new treatments and techniques. This knowledge work was performed in the busy, understaffed world of the mid-20th century hospital. Nurses provided close observation and careful control of the patient, making metabolic research in particular feasible within hospitals. Nurses maintained the cooperation of research patients, a critical aspect to studies involving special diets. Within the hospital, nurses created a “zone of control” around the bedside of research patients, implementing research protocols, closely observing patients and gaining their compliance or cooperation. Using the work of bedside nurses as a historical lens reveals much about the world of medical research and the many factors that contributed to the growth and acceptance of experimentation as a normal part of clinical medicine. Marginalized actors have the agency and power to influence the success or failure of medical research even if they are denied official power. Nursing may hold the solutions to many of the challenges researchers face today.