This publication has been revised to reflect updates made to version 3 of the BehavePlus software, it was originally published as the BehavePlus fire modeling system, version 2.0 User's Guide in June, 2003 The BehavePlus fire modeling system is a program for personal computers that is a collection of mathematical models that describe fire and the fire environment. It is a flexible system that produces tables, graphs, and simple diagrams. It can be used for a multitude of fire management applications including projecting the behavior of an ongoing fire, planning prescribed fire, and training. BehavePlus is the successor to the BEHAVE fire behavior prediction and fuel modeling system. Primary modeling capabilities include surface fire spread and intensity, crown fire spread and intensity, safety zone size, size of point source fire, fire containment, spotting distance, crown scorch height, tree mortality, wind adjustment, and probability of ignition. The User's Guide describes operation of the program. Other papers describe the models and application of the system.