Multidimensional item response theory (MIRT) provides an ideal foundation for modeling performance in complex domains, taking into account multiple basic abilities simultaneously, and representing different mixtures of the abilities required for different test items. This article provides a brief overview of different MIRT models, and the substantive implications of their differences for educational assessment. To illustrate the flexibility and benefits of MIRT, three application scenarios are described: to account for unintended multidimensionality when measuring a unidimensional construct, to model latent covariance structures between ability dimensions, and to model interactions of multiple abilities required for solving specific test items. All of these scenarios are illustrated by empirical examples. Finally, the implications of using MIRT models on educational processes are discussed. (Contains 7 figures.)