Conventional wisdom has long assumed that the major accident risk directly correlated with occupational accidentOccupational accident statistics. Yet, the facts tell a different story. This lesson focuses on major accident riskMajor accident risk indicators that could maintain high levels of awareness, motivation and emphasis on prevention against potential major accidentsMajor accident. The lesson begins by clarifying indicator concepts and definitions. In response to the conceptual confusion surrounding indicator concepts, the authors advocate adopting the terms of precursor indicatorPrecursor indicatorand barrier indicatorBarrier indicator. Then, the lesson explores the need for major accident risk indicatorsRisk indicator, emphasizing their particular characteristics. After that, a comprehensive set of evaluation criteriaEvaluation criteriafor major accident riskMajor accident risk indicators is proposed and discussed to avoid the “garbage in-garbage out” problem. Finally, major accidentMajor accident risk indicators for the nation and enterprise are recommended. The lesson equips readers with the theoretical foundation as well as practices in the development and application of major accident riskMajor accident risk indicators.