This Guideline covers general aspects of measurement uncertainty for quantitative analysis, gives definitions of measurement uncertainty and related terminology and clarifies the role of measurement uncertainty in the interpretation of test results in conformity assessment and in specifying sampling plans for the inspection of lots. This guideline does not address the uncertainty component associated with sampling and focuses on uncertainty contributions which arise in connection with obtaining a test sample from the laboratory sample, taking a test portion from a test sample (i.e. the errors due to the heterogeneity1 between test portions) and the analysis of a test portion in the laboratory. Analytical measurements in food control are often quantitative, but qualitative test results are also relevant. While an evaluation or estimation of measurement uncertainty is not required for qualitative results, it is recommended that laboratories identify factors which have an influence on such test results and establish quality assurance procedures to control relevant effects.