The New York State Department of Health initiated the development of 6 clinical practice guidelines for children under 3 years of age with those developmental conditions most often seen in the state's Early Intervention Program. Separate guidelines were developed for autism/pervasive developmental disorders, communication disorders, Down syndrome, hearing impairment, motor disorders, and vision impairment. Professionals providing early intervention services are confronted with complex issues regarding service provision. This article focuses upon identification and assessment methods recommended by these 6 guidelines. The guidelines specifically emphasize the importance of routine developmental surveillance where primary healthcare providers use both clinical clues and developmental milestones, as signals for further focused screening and in-depth assessment to detect possible developmental conditions. Given the wide variation in timing for reaching specific milestones seen among typically developing children, the use of developmental milestone tables alone may miss opportunities for early identification, which may result in unnecessary “wait and see” recommendations to parents. The use of disorder-specific clinical clues may offer a more efficient and accurate method of developmental surveillance that facilitates earlier identification of infants and young children with developmental disabilities who may benefit from early intervention services.