An exploratory study of Critical Care Nurses Use of Humour was undertaken using an ethnographic approach. During Phase One, fieldwork involving direct observations of nurses and indirect observation of patients was carried out over a four week period. Sixteen semi-structured interviews were conducted during Phase Two. Morreall's Comprehensive Theory of Laughter was used as a conceptual framework. Humour was examined as a coping strategy, method of communication and a nursing intervention, as reflected in a review of the literature. Several questions regarding the nature of humour in a ritical care setting were asked: (1) What factors promote or inhibit nurses use of humour? (2) How are nurses using humour when interacting with other health care team members and (3) How are nurses using humour with patients and family members? Data were analyzed using thematic content analysis. Findings reveal that nurses value and use humour in their interactions with co-workers and patients. The context of humour includesthose factors that enhance or inhibit the use of humour. Nurses identified specific cues and intuition in the assessment of their decision to use of humour. Humour may be interpreted at superficial and various levels of meaning. Humour helps to maintain a balance between patient-care needs and the self-care needs of the nurse. The use of humour represents an important communication strategy, means of coping and nursing intervention.