The 38th Session of the Codex Committee on Food Additives and Contaminants requested the Codex Alimentarius Commission at its 29th Session in 2006 to seek scientific advice from the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) on the risks and benefits of fish consumption: specifically a comparison of the health benefits of fish consumption with the health risks associated with the contaminants methylmercury and dioxins (defined here to include polychlorinated dibenzo-p-dioxins [PCDDs] and polychlorinated dibenzofurans [PCDFs] as well as dioxin-like polychlorinated biphenyls [PCBs]) that may be present in fish. The health risks associated with dietary exposure to these compounds have previously been assessed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The Codex Alimentarius Commission request was driven by growing public concern in recent years regarding the presence of chemical contaminants in fish. Over the same period the multiple nutritional benefits of including fish in the diet have become increasingly clear. The evolving science in this field has led to questions about how much fish should be eaten and by whom in order to minimize the risks of chemical exposures and maximize the health benefits. National authorities have been faced with the challenge of communicating complicated and nuanced messages to consumers and also with questions on how to regulate maximum levels of these chemical contaminants in fish and other foods. Seventeen experts in nutrition toxicology epidemiology dietary exposure and risk-benefit assessment discussed the risks and the benefits of fish consumption. Their task was to review data on levels of nutrients and specific chemical contaminants (methylmercury and dioxins) in a range of fish species as well as recent scientific literature. coveringthe risks and benefits of fish consumption. The review was used to consider risk-benefit assessments for specific end-points including for sensitive groups of the population. The output is intended to provide guidance to national food safety authorities and the Codex Alimentarius Commission in their work on managing risks taking into account the existing data on the benefits of eating fish.