Research on environmental strategies to increase positive peer interactions has been conducted on a wide range of children, including 2- to 5-year-old typically developing children and children with a variety of developmental and social disabilities. Intervention efforts have been successful with both typically developing children and children with mild to moderate disabilities, although research has indicated that for children with more severe social needs, intervention effects may take longer. This "What Works Brief" discusses a number of environmental strategies that teachers and other caregivers can make to promote positive social interactions among children in the classroom. Because the strategies are primarily based on teacher planning and organization, they can be easily adapted to meet the needs of culturally and linguistically diverse children. The brief is arranged in an easy-to-read format that answers the following five questions: (1) What are the environmental strategies to increase positive social interactions?; (2) Why are environmental strategies important for increasing positive social interactions?; (3) Who are the children who have participated in research on using environmental strategies to increase positive social interactions?; (4) Where do I find more information on implementing this practice?; and (5) What is the scientific basis for this practice? The brief contains vignettes that illustrate how specific strategies might be used and includes a one page summary handout for practitioners and families. (SG)