Our aim in developing the objectively driven user-interface of MEGA has been a clutter-free work environment that asks the user for information on a need-to-know basis Although this modular analytical tool looks simple, behind each menu item is a wide range of useful options and tools that come with enhancements that are designed to reduce the amount of time needed for mundane non-technical tasks. Consider, for example, the Sequence Data Explorer. This unique module is hidden away when you don't want it but is always working behind the scenes. It allows you to view the data in various ways, export data subsets, and compute many important basic statistical quantities. Another interesting module is the Genetic Code selector, which allows you to choose the depth at which you wish to work with a code table. With it you can select a desired code table, add new data to and edit the existing code table, view the selected code table in a conventional format, compute the degeneracy for each site in every codon, and compute the number of potentially synonymous and nonsynonymous sites for each codon. In addition, you can always find help by checking the help index.