The authors demonstrate how to use their well-established and documented DIR (Developmental, Individual-Differences, Relationship-Based) model to work with the full range of infant and early childhood challenges. These include interactive problems, such as infants and young children with anxiety disorders, depression, attachment disorders, attentional problems, trauma, and elective mutism; regulatory-sensory processing problems, including infants and young children who are overresponsive and fearful, underresponsive and self-absorbed, sensory craving and overly active and aggressive, as well as those who have difficulty with planning and coordinating action; and neurodevelopmental disorders of relating and communicating, including infants and young children with autism spectrum disorders and other severe developmental challenges.