The NCBI Taxonomy database is a curated set of names and classifications for all of the organisms that are represented in GenBank. When new sequences are submitted to GenBank, the submission is checked for new organism names, which are then classified and added to the Taxonomy database. As of April 2003, there were 176,890 total taxa represented.

There are two main tools for viewing the information in the Taxonomy database: the Taxonomy Browser, and Taxonomy Entrez. Both systems allow searching of the Taxonomy database for names, and both link to the relevant sequence data. However, the Taxonomy Browser provides a hierarchical view of the classification (the best display for most casual users interested in exploring our classification), whereas Entrez Taxonomy provides a uniform indexing, search, and retrieval engine with a common mechanism for linking between the Taxonomy and other relevant Entrez databases.