Builds, manipulates and displays phylogenetic trees. TreeBest is particularly designed for building gene trees with a known species tree and is highly efficient and accurate. It is previously known as NJTREE and has been largely used in the TreeFam database, Ensembl Compara and OPTIC database. Several methods were developed to incorporate species phylogenies in building gene trees. These methods greatly improve the accuracy of gene trees, without adding too much computational overhead.