Evidence is fundamental to science, but finding the right evidence in health education and health behavior (HEHB) is often a challenge. The authors discuss some of the controversies about the types of evidence that should be considered acceptable in HEHB, the tension between the use of qualitative versus quantitative data, the need for measures of important but neglected constructs, and interpretation of data from experimental and nonexperimental research. This article discusses some of the challenges to the use of evidence and describes a number of strategies and some forces encouraging the use of evidence-based interventions. Finally, the authors suggest ways to improve the practice and dissemination of evidence-based HEHB. Ultimately, if evidence-based interventions are not disseminated, the interventions will not achieve their potential. The goal should be to develop more effective interventions and disseminate them to improve the public's health.