BACKGROUND AND OBJECTIVES: No recommendation exists for or against routine use of brief, formal screening instruments in primary care to detect speech and language delay in children through 5 years of age. This review aimed to update the evidence on screening and treating children for speech and language since the 2006 US Preventive Services Task Force systematic review. METHODS: Medline, the Cochrane Library, PsycInfo, Cumulative Index to Nursing and Allied Health Literature, ClinicalTrials.gov, and reference lists. We included studies reporting diagnostic accuracy of screening tools and randomized controlled trials reporting benefits and harms of treatment of speech and language. Two independent reviewers extracted data, checked accuracy, and assigned quality ratings using predefined criteria. RESULTS:We found no evidence for the impact of screening on speech and language outcomes. In 23 studies evaluating the accuracy of screening tools, sensitivity ranged between 50% and 94%, and specificity ranged between 45% and 96%. Twelve treatment studies improved various outcomes in language, articulation, and stuttering; little evidence emerged for interventions improving other outcomes or for adverse effects of treatment. Risk factors associated with speech and language delay were male gender, family history, and low parental education. A limitation of this review is the lack of well-designed, well-conducted studies addressing whether screening for speech and language delay or disorders improves outcomes. CONCLUSIONS: Several screening tools can accurately identify children for diagnostic evaluations and interventions, but evidence is inadequate regarding applicability in primary care settings. Some treatments for young children identified with speech and language delays and disorders may be effective.