Investigated the effect of using multidimensional (MDN) items in a computer adaptive test setting that assumes a unidimensional item response theory model in 2 experiments, using generated and real data in which difficulty was known to be confounded with dimensionality. Results from simulations suggest that univariate calibration of MDN data filtered out multidimensionality. The closer an item's MDN composite aligned itself with the calibrated univariate ability scale's orientation, the larger was the estimated discrimination parameter. (PsycINFO Database Record (c) 2003 APA, all rights reserved).