Many, possibly most, analytical measurements are carried out to assess compliance with a specification or a regulation, for example in the control contaminants in food or the detection of performance enhancing substances in sport. When making an assessment of compliance the presence of unavoidable measurement uncertainty introduces the risk of making incorrect decisions, that is of accepting a batch of material which is outside the specification or rejecting one that is within. This often leads to controversy over whether or not the compliance decision is correct. How to make reliable assessment decisions is described in the EURACHEM/CITAC Guide “Use of uncertainty information in compliance assessment”. The key is the use of decision rules that lead to an unambiguous interpretation of the measurement result and its uncertainty. These decision rules need to be designed to ensure that requirements of the specification or regulation are met and that the risk of making an incorrect decision is acceptable. Ideally they should form part of the specification or regulation.