This “Guidance for Identifying Populations at Risk from Mercury Exposure” is intended to inform countries concerned about the potential health impacts of mercury pollution and, if necessary, to assist in identifying specific subpopulations that may be at risk. The document describes approaches that have been used to estimate exposure to mercury, including biomonitoring and methods that use data on fish consumption and mercury levels in fish. It also describes various environmental models that can be useful in predicting exposure to mercury. In addition, the document provides an overview of the assessment of mercury exposures for some specific exposure scenarios, including occupational and other “hot spot” exposures.This document can be used as a reference for conducting research or investigations regarding mercury exposure.