Aggression occurs regularly on many psychiatric wards; its assessment, prevention and management are fundamental aspects of contemporary psychiatric inpatient treatment. In response to the need to understand aggression in this context a considerable body of research has accumulated, clarifying the demographic and clinical characteristics of patients that contribute to an increased propensity for aggressive behaviour. Concurrent research has identified a range of situational demands, antecedent interactions, functions and precipitants to aggressive behaviour. Rarely has research attempted to understand how these predisposing characteristics sensitise a patient to environmental events, or predispose a patient to act aggressively for particular purposes. This article describes the results of a study that examined the interaction of demographic, clinical, affective and behavioural characteristics with the function of aggressive behaviour. Results revealed several statistically significant relationships. In these instances, the individual characteristics evidently predisposed patients to an increased risk of aggression that satisfied or attempted to satisfy certain functions. Awareness of these associations might assist in the delineation of methods for managing a patient during hospitalisation; patients could be assisted to satisfy psychological needs and staff may be able to provide psychiatric treatment in a manner that reduces the likelihood of aggression.