Intensive Interaction was introduced to a special developmental school in Melbourne, Australia. The school had previously used behavioural and skills-based teaching approaches to underpin the teaching of students with severe/profound intellectual disabilities and autistic spectrum disorders. Video baselines of students involved in classroom interactions were taken before introducing the approach of Intensive Interaction to the school. Following a 30-week period during which the approach was practised routinely in classrooms, further video records were made. These video records enabled comparison to be made against five indicators of student involvement. Professional development using video techniques and structured reflection was initiated with all involved staff. Increases in the student's joint focus, positive affect and interactive involvement were noted. In addition to changes in the communicative involvement of the pupils, the practitioner's communicative involvement was also noted to change. (Contains 5 figures.)