In this issue of Child and Adolescent Psychiatric Clinics , guest editors Drs. Joyce Harrison and Tessa Chesher bring their considerable expertise to the topic of Infant and Preschool Mental Health: Assessment and Treatment. Birth to five is a critical period for building the foundation for good mental health and optimal developmental trajectories, yet very few child psychiatry training programs offer training in infant and preschool mental health. In this issue, top experts bring you up to date with recent advances in this important area.