1. Kevin P. Marks, MD*,† 2. Angela C. LaRosa, MD‡ 1. *Department of Pediatrics, PeaceHealth Medical Group, Eugene, OR. 2. †Division of General Pediatrics, School of Medicine, Oregon Health & Science University, Portland, OR. 3. ‡Department of Genetics and Developmental-Behavioral Pediatrics, Medical University South Carolina, Charleston, SC. * Abbreviations: ASQ: : Ages and Stages Questionnaire ASQ-3: : Ages & Stages Questionnaire, Third Edition ASD: : autism spectrum disorder ECSE: : early childhood special education EI: : early intervention M-CHAT: : Modified Checklist for Autism in Toddlers NPV: : negative predictive value PEDS: : Parents’ Evaluation of Developmental Status PEDS:DM: : Parents’ Evaluation of Developmental Status–Developmental Milestones PPV: : positive predictive value With nearly half of pediatricians still not using standardized screening tools, primary care clinicians should know that the periodic use of general developmental and social-emotional screening tools has been proven to identify promptly two to six times more children (age 0–5 years) with suspected delays than a clinician’s unstructured surveillance alone. After completing this article, readers should be able to: 1. Recognize the many methods available to detect a wide spectrum of developmental and behavioral conditions with screening tools, and the screening schedule recommended by the AAP. 2. Recognize that universal, periodic screening with psychometrically sound developmental-behavioral instruments greatly enhances a clinician’s ability to detect, refer, and monitor children who have evolving developmental and behavioral problems. A pediatric provider’s impression has good specificity but poor sensitivity and thus has difficulty identifying the less obvious delays. 3. Know that children who have false-positive screens (screening test concerning but subsequently ineligible for early intervention or early childhood special education services) are a high-risk group in need of close monitoring and other community services such as evidence-based parenting programs and Head Start. 4. Know the main limitations of applying standardized screening tools into a primary care setting. 5. Be aware that screening measures which adhere to core psychometric and feasibility standards are more likely to perform consistently well and be found sustainable in a primary care setting. Developmental and behavioral problems are among the most common conditions of childhood and adolescence; 15% of children have a developmental disability and 21% have a mental health disorder. If intervention is instituted before kindergarten entrance, many problems can be prevented and the large majority can be ameliorated. In the United States, …