was chosen because of its ability to process very large data sets with low memory load. The system consists of three modules: r.fuzzy.system, r.fuzzy.sets and r.fuzzy.logic. The r.fuzzy.system is not required to work with the two additional modules, which have been designed to perform basic fuzzy operations and overlays and to test intermediate results. All three modules are written in ANSI C using GRASS API and can be run on all platforms that support GRASS GIS. Like other GRASS programs, all modules use command line interface and GRASS Tcl/Tk or wxPython GUI’s.