Article 36 of the 1977 Additional Protocol I to the 1949 Geneva Conventions imposes a practical obligation on states to review the legality of all new weapons, means or methods of warfare before they are used in an armed conflict. To encourage more widespread compliance with the obligation of Article 36 and support confidence building in the area of legal reviews, SIPRI has developed a compendium of existing national Article 36 review procedures. The compendium describes how the review process is conducted in the following countries: Belgium, Germany, the Netherlands, New Zealand, Norway, Sweden, Switzerland, the United Kingdom and the United States. The country presentations are based on responses to a questionnaire that SIPRI submitted to relevant authorities. Each presentation summarizes the format and responsibilities of the reviewing authority, how states interpret the terms of reference and legal obligations of Article 36, and the methods employed to conduct the review.