This report from the NEA Working Group on Human and Organisational Performance establishes a common understanding around the terms human performance (HP), organisational performance (OP), and human and organisational factors (HOF) through a simple model. The model presented illustrates the strong inter-relationship between the terms. It shows that HP includes both human activities and the results of these activities. HOF are the factors which have influence on HP in a positive or adverse manner in a given situation. They can be categorised as human-, technology- and organisation-related factors which are themselves under continuous interaction with each other. The report highlights the need for all managers to develop an understanding that the continuous application of a systemic approach is required to establish and sustain an effective management system and to foster safety culture.