The aim of this document is not to make specific recommendations on preferred estimation techniques; rather, it is to provide a catalogue of available techniques to estimate releases (emissions) from diffuse (non-point) sources, and to summarise the pertinent information needed to apply them. Another aim of this project is to provide a listing of reports and other documentation describing the various methods being used in OECD countries to estimate releases of pollutants to air, water, and land from diffuse sources. This document presents a summary of the major RETs used to estimate non-point emissions to air and water, an overview of OECD country programmes and information on relevant contacts and documentation. This document is an updated version of Part II. It was originally published in 2003 and updated to reflect new and additional information.