In this paper, we propose a new method that uses single and multiple fault simulations to diagnose multiple stuck-at faults in combinational circuits. On the assumption that all suspected faults are equally likely in the faulty circuit, multiple fault simulations are performed. Depending on whether or not a multiple fault simulation results in primary output values that agree with the observed values, faults are added to or removed from a set of suspected faults. Faults which are to be added to or removed from the set of suspected faults are determined using single fault simulation. Diagnosis is effected by repeated additions and removals of faults. The effectiveness of the method of diagnosis has been evaluated by experiments conducted on benchmark circuits. The proposed method achieves a small number of suspected faults by simple processing. Thus, the method will be useful as a preprocessing stage of diagnosis using the electron-beam tester.