The Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) and the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) follow the same general principles and methods for chemical risk assessments, which are published in the reports of both committees. In response to recommendations made by JECFA and JMPR in the 1980s to review the validity of the evaluation procedures then in place, the International Program on Chemical Safety (IPCS) sponsored the preparation of Environmental Health Criteria monographs (EHCs) on Principles for the Safety Assessment of Food Additives and Contaminants in Food (EHC 70) and Principles for the Toxicological Assessment of Pesticide Residues in Food (EHC 104). These monographs and the principles laid out in subsequent reports have served as the basis for the assessments that have been performed by JECFA and JMPR. Although much of the guidance set out in EHC 70 and EHC 104 remains valid, there have been significant advances in chemical analysis, toxicology, dietary exposure assessment and risk assessment approaches for chemicals in food since these monographs were prepared. Accordingly, FAO and WHO initiated a project to update, harmonize and consolidate principles and methods used by JECFA and JMPR for the risk assessment of food additives, food contaminants, natural toxicants and residues of pesticides and veterinary drugs. This monograph is the outcome of that project. The purpose of this monograph is 2-fold: 1) to provide descriptive guidance for JECFA and JMPR to ensure the continuation of transparent and sound expert evaluations of scientific data for risk assessments of chemicals in food; and 2) to inform users of the outputs from JECFA and JMPR such as risk managers and other risk assessment bodies in Member countries and authorities. The monograph addresses the key issues considered by JECFA and JMPR in their food chemical risk assessments.