MacMolPlt: a graphical user interface for GAMESS. MacMolPlt is designed to make it easy to visualize output whenever you need it, without needing to specify special output options to GAMESS or having to manually edit files to create an input file. But it is also designed to produce output of good quality such that it can be used in publications. Generally MacMolPlt will read in all the information it needs from a GAMESS log file, but several other file types are supported and you can also paste in coordinates in a variety of cartesian formats including the formats used in GAMESS output files and Gaussian log files. Once you have data read in you can translate and rotate the molecule using the mouse or manually by entering the molecule center and rotation angles. You can also view orbitals, total electron densities and Molecular Electrostatic Potentials as 2D or 3D surfaces. Depending on the data read in you can animation normal modes, or geometry optimizations, IRC’s and DRP’s (any file with multiple geometeries). MacMolPlt includes a standard interface for opening files, saving files, printing, copying, window movement, and display commands. One very nice feature is tooltip help support. Particularly in the input builder window tooltips are used to further explain each option and indicate the GAMESS input option. Rotation in the display window is controlled by the mouse in the same fashion as Chem3D (thanks to public domain code from Apple). The scroll wheel or Shift+left button zoom the display and the right button or Control+left button translate the molecule. The size of the molecule display and various normal mode display options are controlled via the Display menu. Atomic coordinates and bonds can be viewed in separate windows and bonds may be added via a bond radius and/or an automatic bonding feature. An interactive graphical molecule editor is included. There is also an input builder for GAMESS. It can make it easy to create many GAMESS input files including MO guess and internal coordinates. It doesn’t have all advanced options yet, but works quite well for beginners.