The EU regulation of landfill aims to the safe disposal of waste in the long term. The regulation requires the collection of information on waste characteristics before landfilling. Acid neutralization capacity (ANC) of waste has been included in order to give information on the long-term behaviour of the waste material itself, but it is also important for understand-ing the influence on the surroundings at a landfill (e.g. due to interaction with other materials or landfill leachate). The overall waste body at a landfill needs to become and remain roughly neutral (pH 7-8) in order to avoid any long-term adverse effects in the landfill waste body or in the environment. Adverse effects such as increase in the leachability of metals and organic substances may be caused both by low or high pH values. This report gives background information on the importance of the ANC property and its links to safe disposal. It also provides guidance on inter-pretation of the results and includes a review of critical waste and waste properties with respect to ANC. The target group for this report includes all the stakeholders involved such as the authorities, regulators, waste producers, consultants, and testing laboratories. The results can also be used in the development of national guidelines for implementation of the EU regulations.