A study was undertaken to develop guidelines for the interpretation of the parameters of three multidimensional item response theory models and to determine the relationship between the parameters and traditional concepts of item difficulty and discrimination. The three models considered were multidimensional extensions of the one-, two-, and three-parameter logistic models. The three models were found to have quite distinct definitions of difficulty and discrimination, making it imperative that the user take care to ensure that the characteristics of the model used match the characteristics of the data to which it is applied. The guidelines developed as a result of this study provide information that should be helpful in ensuring that the appropriate model is used for a particular application. (Author)