This International Standard gives requirements and guidance for the estimation and expression of measurement uncertainty (MU) associated with quantitative results in microbiology of the food chain. It is applicable to the quantitative analysis of: products intended for human consumption or the feeding of animals; environmental samples in the area of food production and food handling; samples at the stage of primary production. The quantitative analysis is typically carried out by enumeration of microorganisms using a colony count technique. It is also generally applicable to other quantitative analyses, including Most Probable Number (MPN) techniques and instrumental methods, such as impediometry and flow cytometry. The uncertainty estimated by this International Standard does not include systematic effects ( trueness or bias ).