Clinical Question: Do preschool or young elementary school children (ages 4-8 years) with language impairment who receive complex syntax intervention show improvements in syntax relative to a comparison intervention or control condition? Method: Systematic Review. Study Sources: ERIC, Education Source, PsycINFO, Web of Science, ComDisDome. Search Terms: language impair* OR specific language impairment OR language disorder* AND complex syntax OR complex sentence OR embedded clause* OR dependent clause* OR multiclause* OR subordinate clause* AND interven* OR treat* OR therap* AND child*. Number of Included Studies: 5. Primary Results: (1) Positive outcomes for improved use of complex syntax forms in preschool and young school-age children across all treatment studies; (2) Positive outcomes for conversation-based and narrative-based treatment strategies including conversational recast, expansion, cloze procedures, and modeling; (3) Faster acquisition of complex syntax forms in conversational recast approach to treatment rather than imitation-based approach to treatment; and (4) Limitations across studies included small sample sizes, no randomized controlled study designs, limited use of control or comparison treatment groups, lack of blinding when evaluating outcome measures, inconsistency in complex syntax types targeted, and limited number of intervention approaches. Conclusions: There are a limited number of high-quality studies of complex syntax intervention for young children with language impairment. Of the five studies included in this systematic review, four were suggestive of a need to change clinical practice, one was equivocal, and none were considered compelling (Dollaghan, 2007). Scaffolding methods (recasts, expansions, cloze procedures, and modeling) appeared to be more effective and efficient than explicit instruction using direct imitation when targeting complex syntax. Methods that target complex syntax in ways that are contingent upon the child's utterance, whether in conversational play, picture descriptions, or interactive book reading, seem to be effective. There is a need for additional intervention studies that compare treatment approaches and specific complex syntax types across the developing language and early language for learning time periods in children with language impairment.