Systematic research and practice guidelines addressing preschool psychopharmacological treatment in very young children are limited, despite evidence of increasing clinical use of medications in this population. The Preschool Psychopharmacology Working Group (PPWG) was developed to review existing literature relevant to preschool psychopharmacology treatment and to develop treatment recommendations to guide clinicians considering psychopharmacological treatment in very young children. This article reviews the developmental considerations related to preschool psychopharmacological treatment, presents current evidence bases for specific disorders in early childhood, and describes the recommended algorithms for medication use. The purpose of this effort is to promote responsible treatment of young children, recognizing that this will sometimes involve the use of medications.