Due to previous exposure of items in adaptive testing, items may become known to a substantial portion of examinees. A disclosed item is bound to show drift in the item parameter values. In this paper it is suggested to use a statistical quality control method for the detection of known items. The method is worked out in detail for the 1-PL and 3-PL models. Adaptive test data are used to re-estimate the item parameters, and these estimates are used in a test of parameter drift. The method is illustrated in a number of simulation studies, including a power study.