States need a policy and systems infrastructure that creates a robust continuum of mental health supports and services for infants, young children, and families. One critical element of this continuum is developmentally appropriate diagnosis. "DC:0-5[TM]: Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood" (DC:0-5) is a system for classification of mental health and developmental disorders of infants and young children and is the recommended practice for the clinical conceptualization and diagnosis of children (birth through 5 years old). Over the past 5 years, states have pursued a variety of strategies to integrate DC:0-5 in state policy and systems.