The complete genome sequences of 26 herpesvirus species, some represented by more than one strain, are currently deposited in the public databases. Their combined length totals over four million base pairs. Several additional genomes are in the pipeline, and a host of partial sequence information is also available. Consequently, researchers have a very detailed picture of the genetic content of herpesviruses and their relationships to each other. This review of the herpesvirus phylogenetic tree explains what is currently known about the evolution of this important virus family by proceeding from the twigs, along the branches, boughs and trunk and towards the root. The account focuses naturally on places where the grasp is secure, but also ventures where the bark is slippery and looks out on regions where footholds have not yet been established.