This study aimed to find out more about the day-to-day experiences of parents and therapists who are using the Lidcombe Program and to explore the variability in children’s responsiveness to treatment. Subjects were recruited from five clinics and assessment and therapy data collected on 22 children. Parents of some of these children were interviewed and invited to talk about their experiences of using the treatment with their child. Interviews were also conducted with the recruiting therapists. The experiences of the parents will be discussed in relation to the different components of the program. The questions raised by these interviews and by the child studies will be considered with reference to the literature and some tentative hypotheses formulated that might help explain individual differences. Qualitative research can help to fill in some of the details that must necessarily be left out in large-scale quantitative studies.