RayGUI 2.0 is a new version of RayGUI, a graphical user interface (GUI) to the seismic travel time modeling program of Zelt and Smith <1992>. It represents a significant improvement over the previous version of RayGUI (RayGUI 1.04; Loss et al. <1998a,1998b>). RayGUI 2.0 uses an updated Java version (1.3), and can run on various operating systems (UNIX, Linux, and Mac OS X). Several new functions have been incorporated, including executing the forward and inversion codes of Zelt and Smith <1992>, creating models or adding new parts of models from an ASCII file, graphically adding layers or points, graphically pinching layers, changing the velocity value of a control point, reporting point location and velocity, importing travel-time lists, generating postscript files, exporting the velocity model into an ASCII file, generating 1-D velocity profiles at specified locations, calculating root-mean-square errors between observed and calculated arrivals for selected phases, and accessing the ray trace log, as well as several other new display features.