The Voices of Youth Count initiative's systematic evidence review is the most comprehensive synthesis of evaluation evidence on programs and practices related to youth homelessness to date. This document is one in a series of seven topical evidence summaries derived from the longer evidence review brief. Herein, evaluations of interventions aimed at preventing youth homelessness before it occurs are summarized. Prevention involves a range of policies and programs aimed at identifying youth and children at risk for homelessness and delivering supports and services proactively before the point of crisis. The evidence here includes only impact evaluations designed to assess measurable changes in outcomes due to specific programs and practices. [For the longer evidence review brief, "Missed Opportunities: Evidence on Interventions for Addressing Youth Homelessness," see ED603003.]