We present an original approach for performing Behavioral Fault Simulation (BFS). This approach involves three main steps: (i) the definition of an internal modeling of behavioral descriptions, and the determination of a Fault Model; (ii) the definition of a fault simulation technique ; (iii) the implementation of this technique. We give in this paper a description of the BFS software implementation. We point out how object oriented programming has been used for defining an evolutive and efficient tool. Finally, this paper deals with experiments conducted on ITC'99 benchmarks in order to validate a VHDL behavioral fault simulator (BFS). The effectiveness of the BFS software is clearly demonstrated through the obtained results.