An IRT-based sequential procedure is developed to monitor items for enhancing test security. The procedure uses a series of statistical hypothesis tests to examine whether the statistical characteristics of each item under inspection have changed significantly during CAT administration. This procedure is compared with a previously developed CTT-based procedure through simulation studies. The results show that when the total number of examinees is fixed both procedures can control the rate of type I errors at any reasonable significance level by choosing an appropriate cutoff point and meanwhile maintain a low rate of type II errors. Further, the IRT-based method has a much lower type II error rate or more power than the CTT-based method when the number of compromised items is small (e.g., 5), which can be achieved if the IRT-based procedure can be applied in an active mode in the sense that flagged items can be replaced with new items.