There has been a steady increase in the use of mixed-format tests, that is, tests consisting of both multiple-choice items and constructed-response items in both classroom and large-scale assessments. This calls for appropriate equating methods for such tests. As Item Response Theory (IRT) has rapidly become mainstream as the theoretical basis for measurement, different equating methods under IRT have also been developed. This study investigated the performances of two IRT equating methods using simulated data: linking following separate calibration (the Stocking-Lord method) and the concurrent calibration. The findings from this study show that the concurrent calibration method generally performs better in recovering the item parameters and more importantly, the concurrent calibration method produces more accurate estimated scores than linking following separate calibration. Limitations and directions for future research are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]