Parent child interaction incorporates play situations as an intrinsic part of the therapy process, whereas Lidcombe Therapy uses highly structured activities to facilitate fluency. This study aimed to investigate the impact of different types of play situations on children’s fluency. The fluency of fifteen children under five was measured in both structured and unstructured play situations with a parent. The results indicated that children were significantly more fluent in structured play situations. A measure of the child’s mean length of utterance revealed that this was significantly longer during unstructured play. The implications of this study will be discussed in relation to therapeutic input.