This document provides guidance for performing an exposure assessment – for humans and the environment – based on environmental monitoring data. It covers topics such as environmental levels and distribution of contaminants, ways of using monitoring data in exposure assessments for differing purposes, the collection of data, quality of monitoring activities, as well as several examples of data compilation in member countries and their use in exposure assessment. It describes the basic methodology used to conduct an exposure assessment based on environmental monitoring data, summarising the main facts and issues to be considered. Although there are fundamental differences between human and environmental exposure assessment methodologies, there are still common approaches for using monitoring data, and these constitute the main focus of this document. This document also gives an example of how monitoring data could be used in an exposure assessment, and discusses the possible links between the use of monitoring data and an approach that uses modelling results. The nature of the monitoring data, properties of the measurements, and characteristics of the concentration distributions are discussed from the perspective of their application in exposure assessment.