The 2015 National Content Test (NCT) provides the U.S. Census Bureau with empirical research that contributes to the planning for the content of the 2020 Census race/ethnicity question(s). This report presents findings to the Census Bureau Director and executive staff on research conducted to assess optimal design elements that could be used in question(s) on race/ethnicity. The 2015 NCT is part of the research and development cycle leading up to a reengineered 2020 Census. The test was designed to compare different questionnaire design strategies for key census content areas including race and ethnicity, relationship, and within-household coverage and to provide research for informing content decisions prior to the 2020 Census.