Although the issue of challenging behaviour receives a great deal of attention in educational literature, the exact nature of this behaviour is open to debate. Challenging behaviour can be defined objectively by listing or describing behaviours that are considered disruptive and undesirable. On the other hand, challenging behaviour can be seen as contextual or relative. Based on data from questionnaires and interviews with children and teachers in an Irish primary school, we argue that these approaches to challenging behaviour are not mutually exclusive and find support for an interactive approach. This 'behaviour-in-context' approach involves taking a perspective of behaviour as a response to environmental and individual needs while recognising the objective undesirability of some behaviours. In our study, the development of a mutually acceptable construct of behaviour has emerged as a vital first step in intervention. (Contains 3 tables and 1 note.)