The Integrated Taxonomic Information System (ITIS) is a partnership[1 ] designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagency group within the U.S. federal government, involving agencies from the Department of Commerce to the Smithsonian Institution. It has now become an international body, with Canadian and Mexican government agencies participating. The primary focus of ITIS is North American species, but many groups are worldwide and ITIS continues to collaborate with other international agencies to increase its global coverage.
ITIS provides an automated reference database of scientific and common names for species. As of January 2009, it contains over 592,000 scientific names, synonyms, and common names for terrestrial, marine, and freshwater taxa from all biological kingdoms (animals, plants, fungi, and microbes). While the system does focus on North American species, it also includes many species not found in North America, especially among birds, fishes, amphibians, mammals, many reptiles, and several invertebrate animal groups. Data presented in ITIS are considered public information, and may be freely distributed and copied, though appropriate citation  is requested. ITIS is frequently used as the de facto source of taxonomic data in biodiversity informatics projects.
ITIS couples each scientific name with a stable and unique taxonomic serial number TSN as the "common denominator" for accessing information on such issues as invasive species, declining amphibians, migratory birds, fishery stocks, pollinators, agricultural pests, and emerging diseases. It presents the names in a standard classification that contains author, date, distributional, and bibliographic information related to the names. In addition, common names are available through ITIS in the major official languages of the Americas (English, French, Spanish, and Portuguese).
ITIS and its international partner, Species 2000, cooperate to annually produce the Catalogue of Life, a checklist and index of the world’s species. The Catalogue of Life goal is to complete the global checklist of 1.8 million species by 2011. As of April 2008, the Catalogue of Life has reached 1.1 million species—a major milestone in its quest to complete the first up-to-date comprehensive catalogue of all living organisms.
Of the 483,000+ (January 2009) scientific names in the current database, approximately 210,000 were inherited from the database formerly maintained by the National Oceanographic Data Center (NODC) of the US National Oceanic and Atmospheric Administration (NOAA). The newer material has been checked to higher standards of taxonomic credibility, and over half of the original material has been checked and improved to the same standard.
Biological taxonomy is not fixed, and opinions about the correct status of taxa at all levels, and their correct placement, are constantly revised as a result of new research. Many aspects of classification will always remain a matter of scientific judgment. The ITIS database is updated to take account of new research as it becomes available, and the information it yields is likely to represent a fair consensus of modern taxonomic opinion.
Records within ITIS include information about how far it has been possible to check and verify them. Its information should be checked against other sources where these are available, and against the primary research scientific literature where possible.