The Organization for Economic Cooperation and Development (OECD) released guidance April 25, 2013, on assessing human and ecological exposures to chemicals. Developed by the Joint Meeting of the Chemicals Committee and Working Party on Chemicals, Pesticides and Biotechnology of the OECD, the guidance identifies “key issues” for the use of monitoring data to assess exposure. They include (i) general considerations when using environmental monitoring data for the purpose of exposure assessment, (ii) fundamental properties of monitoring data, (iii) analytical methods, (iv) selectivity and sensitivity, (v) representativeness of monitoring data in the spatial and temporal distribution of environmental concentrations, (vi) consistency of monitoring and modeling approaches, (vii) temporal variation of environmental concentrations, and (viii) density of sampling points. The guidance also includes a discussion of monitoring programs and exposure assessment in Canada, the European Union, Japan, and the United States.