Monitor lizards (genus Varanus) have attracted a great deal of interest--these large and impressive lizards are often the centerpiece of reptile house exhibits. Monitors tend to be fairly wary and difficult to observe--therefore they are not particularly tractable research subjects, but they have nevertheless received an extraordinary amount of attention from devoted students. Varanoid Lizards of the World is a comprehensive account of virtually everything important that is known about monitor lizards, beginning with detailed species accounts and proceeding to various modern comparative analyses. Where possible, people who have had detailed field experience with a particular species have assembled species accounts. In the process of reporting what is known, we also identify what remains to be learned about these lizards. We hope to establish a prototype showing how such a diverse monophyletic group can be exploited both to identify and to understand the actual course of evolution. As such, this effort becomes a protocol for future workers to follow for other groups of closely-related species.