Differential item functioning (DIF) of items has become an important issue in test fairness and equity in large-scale assessments. DIF occurs when subgroups of test takers have equal trait levels but differ in their probabilities of a correct response. DIF items may threaten the validity of test scores for subgroups and can mislead researchers about group differences. Thus, it is critical to identify DIF items. Numerous parametric and nonparametric methods have been proposed for detecting DIF, and a lot of simulation studies have been done to examine the performance of these methods to flag DIF items. However, among these studies, there is little attention to the effects on DIF detection methods of the difference in ability variance between two groups. Thus, the aim of this study is to examine how the difference in ability variance between reference and focal groups affects four commonly used DIF detection methods: (a) logistic regression modeling; (b) Mantel-Haenszel chi-square (MH test); (c) simultaneous item bias test (SIBTEST); and (d) likelihood ratio test. (Contains 2 tables.)