Accommodations influence the measurement of student proficiency. However, with discrepant research findings, it is difficult to evaluate the effects of these practices on the measurement of performance of students with special needs. In this article, we present results from an experimental study investigating the effects of item characteristics on lower and higher reader's differential benefit for two reading-based accommodations on a third-grade mathematics test. Students with lower reading skills differentially benefited from the read-aloud accommodation on items with high mathematics difficulty and high linguistic complexity but did not benefit from a simplified-language accommodation. This study illustrates the need to consider the interaction between item features and student characteristics in accommodations research. Implications for accommodations research as well as practice are discussed. (Contains 1 table and 3 figures.)