Families and front-line care staff are often key agents in helping deliver behavioural interventions to people with intellectual disability and challenging behaviour. The present paper reviews factors which may impact on the effectiveness of such interventions. Both PsychLit and MedLine were used to conduct an automated literature search which included the terms 'learning disability', 'mental handicap', 'mental retardation', 'intellectual disability', 'challenging behaviour', 'families' and 'staff. This search was substantially augmented by additional citations obtained from books and journal articles. The impact of attitudes, beliefs and emotional states as setting conditions for interventions was highlighted. A variety of more general setting conditions related to intervention effectiveness were also identified. Implications for both clinical practice and future research were discussed.