This document presents a summary of the major release estimation techniques (RETs) used to estimate point source emissions to air, water and land, and an overview of RET resources made available by OECD country programmes. The purpose of this document is to provide a catalogue of available techniques for estimating releases (i.e. emissions) from point sources, and to summarise the relevant information needed to apply them. Another objective of this project is to provide a list of reports and other documents describing the various methods being used in OECD Member countries to estimate pollutant releases to air, water, land and transfers from point sources. The first edition of this document was published in 2002, followed by a second edition in 2013. It has now been updated to incorporate new and additional information.