Published in 1994, the Diagnostic Classification System for Mental Health and Developmental Disorders of Infancy and Early Childhood (DC:0-3) by the organization Zero to Three, is the first developmentally oriented system for diagnosing mental health and developmental disorders in infants and toddlers. The proposed diagnostic classification is the result of the work of an interdisciplinary team of specialists in infant and toddler mental health.

The revised edition of the "Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood (DC:0-3R)" is based on empirical research, clinical observations, and clinical applications internationally since 1994. The revised edition of DC:0-3 is designed to assist mental health professionals and others in order to:

- Recognize the challenges posed by the mental health and development of infants and toddlers
- Understand the role and impact of relationships and environmental factors in the emergence of mental and developmental disorders
- Use diagnostic criteria effectively for classification and intervention
- Work more effectively with parents and other professionals to design appropriate therapeutic interventions.

DC:0-3R enhances the clinician's ability to prevent, diagnose, and treat mental health issues in the early years of a child's life, recognizing and describing disorders that are not included in other classification systems, and highlighting ways for more effective intervention.

Mental health clinicians, counselors, physicians, nurses, early intervention specialists, preschool educators, as well as researchers will find DC:0-3R an essential guide for clinical assessment and therapeutic planning for infants, toddlers, and their families across a wide range of settings.