With the aim of clarifying critical care nursing, six critical care nurses, working in a Swedish intensive care unit (ICU) were each asked to narrate a care situation with which they had been satisfied or dissatisfied. The stories were tape-recorded and analysed using a phenomenological-hermeneutic approach inspired by the philosophy of Ricoeur. The themes uncovered in the analysis describe the nurse's role of advocacy as: to build a caring relationship, to carry out a commitment, to empower, to make room for and interconnect, to be a risk-taker, to be a moral agent and to create a trusting atmosphere conducive to recovery. The meaning of the role of advocacy lies in a moral and existential response to another human being, an expression of caring. Advocacy rests on the patient-nurse relationship and occurs as an outspoken demand of another human being whose autonomy is threatened. The results are discussed from the ethical perspectives of Lögstrup, Watson's concept of care, and existential advocacy as expressed by Gadow.