Mercury is considered a global pollutant and it has been concluded that a significant portion of humans and wildlife throughout the world are exposed to methyl mercury at levels of concern. The Governing Council of UNEP has concluded that long-term international action is required. Most of the measures needed to reduce emissions will lead to costs to society. However, mercury pollution also results in costs to society including for example damage costs from negative impacts on human health and the environment, loss of income from reduced commercial fisheries, administrative costs for scientific research and development, control and risk communication. The aim of this report is to present an estimate of the socio-economic costs of continued mercury contamination of the environment as an input to the global considerations on what international long-term action should be taken. The study contains an analysis of the damage costs of continuing mercury pollution without any further measures until 2020. The analysis has mainly focussed on IQ losses due to the exposure to methyl mercury via ingestion of contaminated fish. Other human health, social and environmental damages are also discussed as are costs of controlling mercury emissions. Furthermore, societal benefits of reducing mercury emissions are presented for two emission reduction scenarios.