Since fiscal year 1998, the Title V, Section 510 program has allocated $50 million annually in federal funding for programs that teach abstinence form sexual activity outside of marriage as the expected standard for school-age children. A new impact report from Mathematica's congressionally mandated multi-year evaluation of four abstinence education programs finds that the programs had no effect on the sexual abstinence of youth. But it also finds that youth in these programs were no more likely to have unprotected sex, a concern that has been raised by some critics of these programs. The following are appended: (1) Supporting Tables for the Impact Analysis; (2) Outlines of Curricula Used by the Four Programs Included in This Report; (3) Survey Questions Underlying the Outcome Measures Used for the Final Impact Analysis; (4) Estimated Impacts for Selected Subgroups; and (5) Program Impacts on Potential Mediators of Teen Sexual Activity (Measured from the Final Follow-Up Survey). (Contains 18 tables and 15 figures.)