In the United States, there exist a multitude of different approaches to reducing adolescent sexual risk-taking, unintended pregnancy, childbearing, and sexually transmitted disease, including HIV. While many of these approaches have some positive effects upon some outcomes (such as greater knowledge), only some of these programs actually delay the initiation of sex, increase condom or contraceptive use, and reduce unprotected sex among youth. This article summarizes a review of 73 studies and their respective programs, and describes four groups of programs which have reasonably strong evidence that they delay sex, increase condom or contraceptive use, or reduce teen pregnancy or childbearing. These four groups of programs include (a) sex and HIV education curricula with specified characteristics, (b) one-on-one clinician-patient protocols in health settings with some common qualities, (c) service learning programs, and (d) a particular intensive youth development program with multiple components.