PURPOSE: This study was conducted to identify ICU nurses' knowledge of the five moments of hand hygiene and the ambiguity of these moments when demonstrating hand hygiene.METHODS: The subjects were 200 intensive care unit nurses at a university hospital . Data was collected using self-report questionnaires, translated according to the instructions of training films developed by WHO, and analyzed using descriptive statistics and ranking tests.RESULTS: The highest number of correct answers was regarding the moment before contact with a patient and the lowest was regarding the moment after contact with a patient. The rate of providing wrong answers regarding required moments of hand hygiene was high.CONCLUSION: The study identified ICU nurses' knowledge of specific moments of hand hygiene; they had difficulty differentiating between the moments that happened simultaneously, i.e. after touching a patient, and that patient's surroundings, and there was ambiguity concerning patient areas and medical treatment areas. It was concluded that it is necessary to educate nurses regarding both required and unrequired moments of hand hygiene and to ensure that they can distinguish between these moments.