Before 1994, the more subjective threatened species categories used in IUCN Red Data Books and Red Lists had been in place, with some modification, for almost 30 years. In 1989, development of a more objective approach began, and in 1994 the first IUCN Red List Categories and Criteria (version 2.3) were adopted by IUCN Council.
A review process began in 1996 to address improvements to the criteria identified by Assessors. This resulted in a revised version of the criteria (version 3.1), which was adopted by IUCN Council in February 2000. The IUCN Red List Categories and Criteria. Version 3.1 provides a clearer, more open and easy-to-use system.
The conversion of all assessments on the IUCN Red List that use the 1994 system (version 2.3) to the current system (version 3.1) will take time. Meanwhile, the current IUCN Red List includes assessments using both the 1994 system and the 2001 system. To avoid confusion, all assessments using the 2001 Red List Categories and Criteria are indicated by a 'ver 3.1 (2001)' hyperlink, and all assessments using the 1994 Red List Categories and Criteria are indicated by a 'ver 2.3 (1994)' hyperlink.
All new assessments and reassessments on the IUCN Red List use the 2001 IUCN Red List Categories and Criteria. Version 3.1.
In 2012 the second edition of this publication was released. In this edition, the IUCN Red List criteria have not changed (i.e., the first edition can still be used). However, some of the Annexes within this document have been modified as a result of changes in the required supporting information for IUCN Red List assessments.
Assessments from 1996-2000 that have not been converted over to the revised system use the 1994 Red List Categories and Criteria. For a comparison of the 1994 and the 2001 Red List Categories and Criteria, click here.
A range of documents and tools are available to guide Assessors through using the IUCN Red List Categories and Criteria, the supporting information requirements for assessments, using Red List data, the Red List Index, etc.
For access to all of these documents, go to the Key Documents page on this website.
Over the last decade there has been growing interest in countries using the IUCN Red List Categories and Criteria for national Red List assessments. In response to this interest, IUCN developed guidelines on how to apply the IUCN Red List Criteria appropriately for sub-global level assessments.
Since the first version of the Guidelines for Application of the IUCN Red List Criteria at Regional Levels was published in 2003 (version 3.0), these guidelines have been reviewed. In 2012, the Guidelines for Application of the IUCN Red List Criteria at Regional and National Levels. Version 4.0 was released. In version 4.0, the guidelines have not changed substantially (i.e., version 3.0 can still be used), however the presentation of the guidelines has been made clearer.
Please note that national or regional assessments are NOT eligible for inclusion on the IUCN Red List, unless they are for endemic species.
The National Red Lists website allows national and regional Red List data from around the world to be accessed from one central place. This website includes a searchable species database, a library of downloadable documents, a network of individuals involved in national/regional Red Listing around the world, and a discussion forum for specific queries.
The IUCN Red List Index (RLI) measures overall trends in extinction risk for groups of species based on genuine changes in their Red List status over time. Further information about the RLI and how it is calculated can be found in the Red List Index section on the Publications and Links page.
A tool to help you to calculate the RLI from suitable data is also available from the IUCN Red List Guidance Documents page in the Red List Training section on this website.