PROJECT SUMMARY Between 7-10% of children have developmental language disorders (DLD) without other developmental concerns at kindergarten entry,1,2 which place them at significant risk for poor academic and social outcomes across the school years and into adulthood.3 Brief naturalistic intervention can significantly increase expressive vocabulary in toddlers with receptive and expressive language delays,4 but it is not sufficient to reduce the developmental gaps in vocabulary or syntax.5 No studies to date have examined the potential of sustained early intervention for maximizing language outcomes. The proposed study will: (a) evaluate the effects of a sequential language intervention on the vocabulary and grammar of young children at risk for developmental language disorder (DLD) and (b) examine moderators and mediators of intervention effects. The proposed hybrid intervention (EMT-SF) provides an empirically-supported intervention, Enhanced Milieu Teaching (EMT), blended with a theoretically-motivated, sentence-focused (SF) sequence of treatment targets6,7 and new input modification strategies.8,9 The central hypothesis is that intervention will result in greater vocabulary and grammar outcomes for children at high risk for DLD in the treatment group. The proposed research is a stratified randomized clinical trial comparing the effects of the EMT-SF intervention, implemented by parents and therapists, to a control condition and enrolling 108, 30-month-old children and their parents. Four specific aims guide the study: 1. Compare differences in vocabulary and grammar outcomes in treatment vs control children at 48 months of age. 2. Determine the extent to which parent language input and parental use of intervention strategies mediate child language outcomes. 3. Determine the extent to which child-level factors and child progress during intervention predict language outcomes 4. Determine the extent to which the intervention impacts broader aspects of spoken language and behavior related to literacy and school readiness (decontextualized language, narrative abilities, behavior problems) (exploratory). IMPACT: This study will determine if sustained early intervention can reduce the long-term risks of DLD, will inform developmental theory, and provide critical information that may transform preschool service delivery models.