Teens typically fail to use contraceptives consistently, which contributes to high rates of unintended pregnancy and sexually transmitted infections (STIs) among this age group. Existing research has focused primarily on how teens' own characteristics are related to contraceptive use, but has paid less attention to how the characteristics of teens' relationships and partners might influence contraceptive use and consistency. Using survey data from high school students, this "Fact Sheet" presents findings from recent Child Trends research examining how multiple dimensions of teens' sexual relationships and sexual partners may influence their contraceptive use and consistency. A better understanding of these issues can help parents, program providers, and teens themselves reduce high rates of unintended teen pregnancy, child-bearing, and STIs in the United States. (Contains 3 figures.) [This "Fact Sheet" is based on an article titled "Contraceptive Use Patterns Across Teens' Sexual Relationships: The Role of Relationships, Partners, and Sexual Histories," published in the August 2007 issue of "Demography".]