The study sought to investigate the perceptions and experiences of nurses practising in adult intensive care units (ICUs) with regard to medical futility. A qualitative exploratory descriptive design was used, providing a framework which enabled information to be gathered on a relatively undefined phenomena. Data were gathered via semi-structured interviews with seven intensive care nurses. Findings concluded that there is no 'one size fits all' definition of medical futility. To arrive at the decision whether treatment is futile, participants want to understand patients' views on treatment limitation. In some ICUs, 'the decision' about whether to cease or continue treatment is unilaterally made by medical staff, raising concerns about value laden judgement. Nurses experience frustration with having to administer treatment with which they do not agree and may actually leave intensive care nursing because of their moral conflict. There are opportunities for nurses to have input into 'the decision', but they must have a cogent and articulate approach to be heard. Once treatment is deemed to be futile, nurses play a key role in treatment withdrawal and can have a significant impact on the patient and family experience if they manage the situation well; this nursing role in medically futile situations and treatment withdrawal is detailed. 'Medical futility' is not easily defined. Understanding patients' views about treatment limitation is important in deciding whether treatment is medically futile. To do this, an inclusive decision making process should be developed by ICUs which incorporates nursing and family input. Experienced ICU nurses can have a significant impact on the management of futile cases; they need to share their understanding of the processes surrounding medical futility and assist junior nurses in negotiating the difficult challenges encountered in decision making and treatment withdrawal.