This article describes the crucial role of research nurses in studies coordinated by the NHS Blood and Transplant Clinical Trials Unit (CTU), using two recent trials studying platelet transfusions in adults and neonates as examples. CTU studies are coordinated by trial managers, most of whom are or were registered nurses, which supports relationships with research nurses in participating hospitals. During trials the CTU sustains research nurses with ongoing education and training, and establishes cooperative working between nurses and the unit, and between nurses in different locations. Regular feedback from research nurses guides the design and management of clinical trials.