Introduction: nurses working in hematopoietic stem cell transplantation (HSCT) units carry out highly specialized work, because, aside from its complexity, transplantation is involves a set of procedural techniques. Objective: to describe the tasks carried out by nurses working in HSCT units and classify them according to the frame of reference of a Brazilian HSCT unit. Method: a qualitative descriptive research study was carried out in May 2011 with twelve nurses, using systematic observation techniques of their daily activities for a total of seventy-seven hours. Results: staff nurses principally carry out care-giving activities and education, whereas tasks related to cooperation, coordination, and supervision are mainly carried out by the nurse manager and visiting nurses. Conclusion: nurses carry out all manner of tasks. They take care of all transplant patients, their treatments, and the services they are provided. In some ways, nurses go beyond the limits of the profession.