The United States has experienced remarkable improvements in public health and medical progress throughout much of the twentieth century, including major advances in pharmaceutical and medical device innovation and gains in life expectancy. These improvements, however, have not been accessible to all parts of U.S. society. Substantial disparities in life expectancy, health, and health care persist. Although many actors-including health care systems, insurers, health care providers, and patients-contribute to these disparities, bias, discrimination, and stereotyping during the clinical encounter also explain health care disparities. Experts recommend reducing fragmentation in health care systems, improving awareness on the part of health care providers of these problems, strengthening culturally competent approaches to the delivery of health care, and increasing the diversity of the health care workforce, as strategies to reduce health care disparities. A core component in recommendations to address healthcare disparities is the involvement of the community: specifically, the involvement of community health workers (CHWs). The RTI International-University of North Carolina at Chapel Hill Evidence-based Practice Center (RTI-UNC EPC) conducted a systematic review on outcomes of CHW interventions. The review addressed four key questions (KQs): KQ 1. How do CHWs interact with participants? Specifically, what is the place of service, type of service, type of educational materials used, duration of interaction with participants, and length of followup? KQ 2. What is the impact of CHWs on outcomes, particularly knowledge, behavior, satisfaction, health outcomes, and health care utilization? KQ 3. What is known about the cost-effectiveness of CHWs for improving health outcomes? KQ 4a. What are characteristics of training for CHWs in the outpatient setting? KQ 4b. Are particular training characteristics associated with improved outcomes for patients?