ISO/IEC 20000 is the first international standard for IT Service Management. It is based on and is intended to supersede the earlier British Standard, BS 15000.
Formally: ISO 20000-1 ('part 1') "promotes the adoption of an integrated process approach to effectively deliver managed services to meet the business and customer requirements
ISO 20000-2 ('part 2') is a 'code of practice', and describes the best practices for service management within the scope of ISO 20000-1. It comprises the same sections as 'part 1' but excludes the 'Requirements for a Management system' as no requirements are imposed by 'part 2'.
ISO 20000, like its BS 15000 predecessor, was originally developed to reflect best practice guidance contained within the ITIL (Information Technology Infrastructure Library) framework, although it equally supports other IT Service Management frameworks and approaches including Microsoft Operations Framework and components of ISACA's CobIT framework. It comprises two parts: a specification for IT Service Management and a code of practice for service management. The differentiation between ISO 20000 and BS 15000 has been addressed by Jenny Dugmore  .
The standard was first published in December 2005.