Purpose: This article describes guiding principles in early intervention (EI) and demonstrates how speech-language pathologists (SLPs) can apply these principles to best serve infants and toddlers with communication and related problems and their families. Method: Four principles guide the implementation of speech-language pathology services. EI services are services that are (a) family centered and culturally and linguistically responsive; (b) developmentally supportive, promoting children's participation in their natural environments; (c) comprehensive, coordinated, and team based; and (d) based on the highest quality evidence available. Actual clinical scenarios are presented to illustrate each principle. Results: The four principles provide a framework for the wide range of roles and responsibilities assumed by SLPs in EI: (a) screening/evaluation/assessment, (b) goal setting and intervention, (c) consultation with and education for team members, (d) service coordination, (e) transition planning, and (f) advocacy. Conclusion: It is critical that families of infants and toddlers who are at risk for, or who have been diagnosed with, communication disorders receive all necessary services and supports. EI services should be tailored to the individual and the changing needs, preferences, and priorities of each family. The earlier services are provided, the more likely is the child's chance to develop effective communication.