This declaration summarizes the scientific and technical conclusions presented by four expert panels in their critical synthesis manuscripts and in plenary sessions at the Eighth International Conference on Mercury as a Global Pollutant, convened in Madison, Wisconsin, USA, on 6–11 August 2006. The 1150 registered participants in this conference constituted a diverse, multinational body of scientific and technical expertise on environmental mercury pollution. This declaration conveys the panels' principal findings and their consensus conclusions on key policy-relevant questions concerning atmospheric sources of mercury, methylmercury exposure and its effects on humans and wildlife, socioeconomic consequences of mercury pollution, and recovery of mercury-contaminated fisheries.