An intelligent EB test system for automatic VLSI fault tracing is described. In order to control the system flexibly, we use two parameters: the reliability of measurement P and the importance of the interconnection I. The former represents the degree of faith in information obtained through measurement. The latter expresses the degree of reduction in the number of probing points after measuring the current selected interconnection, as compared with the case where the measurement of the current selected interconnection is skipped. Utilizing the two parameters, the system judges whether information obtained through measurement is reliable or not, and controls the fault-tracing sequence. Besides, when the fault tracing is finished, the reliability of the fault-tracing path Q is evaluated. This parameter indicates the probability that the localized origin is the true origin of the faulty signal detected on the external pad. The system is implemented on a production system. We simulate the fault tracing on the circuit data of a self-made microprocessor to show its validity.