There are many different approaches to intervention aimed at facilitating the social and communicative abilities of children with Autistic Spectrum Disorders (ASD). Behavioural interventions seek to improve the social and communicative abilities of children with ASD through interaction. Recently there has been a move towards naturalistic behaviour-based interventions (NBI). Despite this trend there has been relatively little research into the mechanics of this approach. This study investigated an intervention programme aimed at pre-school children with ASD to identify, first, the different contexts of interaction during the intervention and, second, the communication strategies developed by the practitioners. Eight children were followed through the intervention programme, resulting in 21 hours of video data. Ten contexts of interaction were identified, including play, directed tasks and transitions. Practitioners combined structure and directiveness in their communication strategies. Six levels of directiveness were identified, ranging from observing to prompting. A distinction was made between emergent and imposed structures. The interaction strategies, within this dataset, which resulted in prolonged and varied discourse were based on dynamic emergent structures and in the mid range of the directiveness continuum. The findings are discussed with reference to how strategies may be identified and implemented by practitioners within NBI. (Contains 3 tables and 1 figure.)