Developing self-regulation at an early age is important for children's success in school and in life. Self-regulation involves the ability to remember instructions, shift attention from one thing to another, and reduce the intensity and frequency of impulsive emotions and behaviors. "Red Light, Purple Light" is a preschool program that includes music and movement games aimed at fostering self-regulation skills in young children. The What Works Clearinghouse (WWC) reviews existing research on educational interventions to identify evidence-based programs and practices. This WWC intervention report summarizes the available evidence on the effects of "Red Light, Purple Light" on student outcomes. [For the Intervention Brief, see ED624626.]