This paper describes a number of global regulations dealing with very fine ambient particulate matter, PM(2.5) and PM(10) and the measurements aspects of PM(2.5) emission measurement methods for stationary sources, particularly of dilution techniques that promote simulation of atmospheric transformation of stack gases allowing for the use of the resulting near-ambient emission data in source apportionment and health risk studies, along with the current progress on international standardization of source PM(2.5) measurement methods. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.