Background: Aggression is a common type of problem behaviour in clients with mild to borderline intellectual disability who live in a residential facility. We explored contextual events that elicit aggressive behaviour and variables that were associated with such events. Method: Respondents were 87 direct-care staff members of 87 clients with aggressive behaviour who lived in a residential facility. Staff members completed the "Contextual Assessment Inventory" (CAI) and a questionnaire on demographic information and types, frequency and severity of aggressive behaviour. Internal consistency of the total CAI was excellent (alpha = 0.95), and Cronbach alpha's for the CAI sub-scales ranged from 0.75 to 0.93. Inter-rater agreement for the CAI could be considered good (mean intra-class correlation coefficient = 0.63). Results: Both social and task-related events were reported to evoke aggressive behaviour of clients most often. Negative interactions, task characteristics and daily routines relatively often evoked aggressive behaviour while an uncomfortable environment, medication, illness and physiological states (i.e. physical and biological events) evoked aggressive behaviour least often. Mean CAI sub-scale scores were significantly related to gender, IQ and frequency of aggressive behaviour. Conclusion: The present study extends our knowledge regarding events that are associated with an increased probability of aggressive behaviour. Knowledge of these contextual variables may be helpful in designing programmes (e.g. applied behaviour analysis, social skills training and cognitive behavioural therapies) for the management and prevention of aggressive behaviour in clients with mild to borderline intellectual disability who live in a residential facility.