This European Standard specifies the characteristics of a categorial structure and the minimal domain constraints required for conformance, in order to support the exchange of meaningful surgical procedure information between different national terminologies of surgical procedures using different national languages within Europe. Categorial Structures supports interoperability by providing common frameworks with which to a) develop terminologies that are able to be related to each other and b) to analyse the properties of different terminologies to establish the relationship between them. This standard is applicable to: organisations involved with the development or maintenance of classifications and coding systems for medical procedures, namely for multipurpose coding systems on a national or international level organisations developing and maintaining software tools allowing natural clinical language expressions analysis, generation and mapping to the main existing classifications of surgical procedures. The standard has been developed for use as an integrated part of computer-based applications and for the electronic healthcare record. It would be of limited value for manual use. The standard itself is not suitable for or intended for use by, the individual clinician or hospital administrator. It is not the purpose of this standard to standardise the end user classification or to conflict with the concept systems embedded in national practice and languages. This standard is applicable to surgical procedures in all surgical disciplines.