TreeBASE is a repository of phylogenetic information - specifically user-submitted phylogenetic trees and the data used to generate them. TreeBASE accepts all types of phylogenetic data, such as trees of species, trees of populations, trees of genes, representing all biotic taxa.

Data in TreeBASE are exposed to the public if they are used in a publication that is in press or published in a peer-reviewed scientific journal, book, conference proceedings, or thesis.

Data for publications still in preparation or in review can be submitted to TreeBASE but will only be available to the publication editors or reviewers.

As of early 2010, TreeBASE contains 6,500 trees in 2,500 publications written by 4,500 different authors. These trees have 135,000 distinct taxon labels that map to approximately 60,000 distinct taxa.