One of the goals of the NIH Toolbox for Assessment of Neurological and Behavioral Function was to identify or develop brief measures of emotion for use in prospective epidemiologic and clinical research. Emotional health has significant links to physical health and exerts a powerful effect on perceptions of life quality. Based on an extensive literature review and expert input, the Emotion team identified 4 central subdomains: Negative Affect, Psychological Well-Being, Stress and Self-Efficacy, and Social Relationships. A subsequent psychometric review identified several existing self-report and proxy measures of these subdomains with measurement characteristics that met the NIH Toolbox criteria. In cases where adequate measures did not exist, robust item banks were developed to assess concepts of interest. A population-weighted sample was recruited by an online survey panel to provide initial item calibration and measure validation data. Participants aged 8 to 85 years completed self-report measures whereas parents/guardians responded for children aged 3 to 12 years. Data were analyzed using a combination of classic test theory and item response theory methods, yielding efficient measures of emotional health concepts. An overview of the development of the NIH Toolbox Emotion battery is presented along with preliminary results. Norming activities led to further refinement of the battery, thus enhancing the robustness of emotional health measurement for researchers using the NIH Toolbox. Neurology In everyday terms, the word "emotion" evokes connotations of strong feelings, often negative and distressing when they tax our capacity to maintain our poise. It is unpleasant when we are extended beyond our usual resources by stressful life events including poverty, unemployment, oppression, discrimination, and disease. However, positive emotions can be reflections of well-being in our lives, and positive social relationships can buffer stress and enhance health. Recognizing the full spectrum of emotional life and its impact on health, the mandate for the NIH Toolbox was to develop assessments with a broad focus, beyond just negative emotion, or emotional distress. The original Request for Proposals alluded to several additional aspects of the experience and expression of emotion relevant to health in the general population including the importance of psychological well-being, the role of important aspects of positive functioning, such as adaptability, resilience, and self-efficacy, and the importance of the interpersonal and social context in which emotions arise and may be expressed.Feedback provided through an NIH Toolbox Expert Request for Information (RFI) was also consistent with this desire for a broad emphasis on emotional health. As part of this RFI, we obtained input from 147 experts (64% of 232 invited experts), including key opinion leaders from the NIH research program staff and NIH-funded investigators with a broad focus in neurologic and behavioral