In June 2001 the Species 2000 and ITIS organisations decided to work together to create the Catalogue of Life. They declared a target for completing coverage for all 1.75 million known species by 2011. The two organisations remain separate and different in structure. However, by working together in creating a common product, the partnership has enabled us to reduce duplication of effort, make better use of resources, and to accelerate production.

The Catalogue is published as two products:

• Species 2000 & ITIS Catalogue of Life: Annual Checklist
The Annual Checklist is published each year as a fixed edition that can be cited and used as a common catalogue for comparative purposes by many organisations. A copy is on CD-ROM, which is distributed free of charge, and an identical copy is on the website at www.catalogueoflife.org/annual-checklist/. Archived earlier editions are also available on the Species 2000 website.

• Species 2000 & ITIS Catalogue of Life: Dynamic Checklist
The Dynamic Checklist is a virtual catalogue operated on the Internet and available both for users and as an electronic web-service at www.catalogueoflife.org/dynamic-checklist/. The Dynamic Checklist harvests taxonomic sectors and associated strands of hierarchical classification dynamically from the source databases across the internet. The Dynamic Checklist is presently less extensive than the Annual Checklist because fewer taxonomic sectors have been connected so far.

It differs in concept from the Annual Checklist in that: (i) the taxonomic records may be updated and the catalogue changed more frequently than in the Annual Checklist and (ii) the Dynamic Checklist contains additional regional species checklists (such as the Regional Checklist - Europe, effectively a Pan-European Species Checklist) not included in the Annual Checklist.