PRay is a graphical user interface for interactive displaying and editing of velocity models for seismic refraction. It is optimized for editing rayinvr models but can also be used as a dynamic viewer for ray tracing results from other software. The main features are the graphical editing of velocity and depth nodes; fast switching of displayed rays, stations and the rayinvr configuration; running of user defined shell scripts; linking to phase picking software and editing of phase numbers. PRay is open source software written in the scripting language Perl; runs on Unix like operating systems including Mac OS X; provides a revision controlled source code repository for community development and can be downloaded from http://aforge.awi.de/gf/project/pray/.