Pupils with autism spectrum disorder (ASD) received 6 months of intensive interaction or treatment as usual. They were assessed for behaviour problems at the start and end of the period, and changes were related to child and parent factors. Intensive interaction did not offer any greater advantages to child behaviour than treatment as usual. However, intensive interaction was more effective for pupils with less challenging behaviour. Levels of depression in mothers were related negatively to changes in child behaviours. These data suggest that intensive interaction may be of limited utility for reducing problem behaviours of pupils with ASD, but that the approach could be effective with less behaviourally challenging pupils and that levels of parent distress may reduce its impact.