[en] The intervention levels for evacuation, sheltering and iodine blockade still differ in many countries, although international organisation like IAEA, NEA or ICRP aspire to harmonise them on an international level. Even if the dose values of the limits are in agreement, they are not necessarily comparable because the type of dose (projected dose, averted dose), the respected exposure pathways (external dose, inhalation, ingestion) or the integration time might differ significantly. The question is raised, how can harmonisation being achieved? International organisations recommend 'operational intervention levels' (OILs) for promptly assessing the results of environmental monitoring and to decide on protective actions. OILs are measurable values derived from dose limits. Best examples are the derived intervention levels for food and feed in the codex alimentarius or by the EC, which limit the ingestion dose to about 5 mSv/a. This paper discusses the properties and potential use of OILs, identifies and derives useful OILs and addresses their benefit in practise both for early and later countermeasures. Furthermore it is discussed whether OILs might be a useful tool to overcome national differences in intervention levels because an OIL value covers a relative wide range of the projected dose due to the uncertainty of the parameters needed for derivation. (author)