This document specifies requirements and gives 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. This document is also generally applicable to other quantitative analyses, including: — most probable number (MPN) techniques; — instrumental methods, such as impediometry, adenosine triphosphate (ATP) and flow cytometry; — molecular methods, such as methods based on quantitative polymerase chain reaction (qPCR). The uncertainty estimated by this document does not include systematic effects (bias).