Fault simulators are used to evaluate the quality of a test pattern generated. So far, most fault simulators did not handle bus conflicts properly. We analyzed . all possible bus conflicts when test patterns are applied to a circuit with bus structure and categorized bus conflicts into various types. Also. we proposed an efficient method to identify various types of bus conflicts. The fault simulator which employs the proposed method can evaluate the quality of test patterns generated and also can avoid destruction of bus drivers due to bus conflicts hy warning the use of test patterns which cause bus conflicts. The proposed method can also be incorperated into a test pattern generator so that it can generate conflict-free test patterns.