The focus for this lecture considers key concepts around dosage and active ingredients when providing language interventions, with speakers Professors Cristina McKean and Pauline Frizelle. This lecture examines the available evidence about the characteristics of child language interventions which make them work or not. It is of relevance to all therapists working with children and young people with language difficulties, but also contains key concepts about dosage and active ingredients which will be of relevance to all therapists who provide language interventions.