&NA;The article presents a rationale for and components of a developmental systems model to guide early intervention programs for vulnerable children and their families. Core principles emphasizing a developmental framework, integration, and inclusion, as well as related principles, are expressed in the context of a multicomponent interactive system. A central organizing feature of the model is its focus on maximizing family patterns of interaction by addressing potential stressors related to risk and disability conditions. It discusses the importance of consistency across the model's conceptual framework, knowledge based on developmental and intervention science, and professional practices and experience.