In 2010, the U.S. Department of Health and Human Services (HHS), under a contract with Mathematica Policy Research, initiated the Pregnancy Prevention Research Evidence Review (PPRER) to identify rigorously evaluated and effective teenage pregnancy prevention program models. The review effort has established scientific standards to assess the credibility of evaluation findings, and uses those standards to assess completed evaluations of programs designed to improve teenage outcomes related to sexual activity, contraceptive use, sexually transmitted infections (STIs), pregnancy, or birth. Each completed evaluation is rated as having high-, moderate-, or low-quality evidence. Low-quality evidence is not used to determine program effectiveness.