Previous AMAP assessments of mercury in the Arctic published in 1997 and 2002, reported that a substantial amount of the mercury in the Arctic arrives via long-range transport from human sources at lower latitudes and that, owing to their traditional diet some Arctic populations receive high dietary exposure to mercury, raising concern for human health. This situation prompted calls by the Arctic Council for global action to reduce mercury emissions. The effects of mercury on biota may be particularly relevant for species at the limits of their tolerance to other stressors. The overarching goal of this assessment was therefore to update information relevant to answering the question: What controls mercury levels in the Arctic and what are the effects on Arctic biota?