Gender fairness in testing can be impeded by the presence of differential item functioning (DIF), which potentially causes test bias. In this study, the presence and causes of gender-related DIF were investigated with real data from 800 items answered by 250,000 test takers. DIF was examined using the Mantel-Haenszel and logistic regression procedures. Little DIF was found in the quantitative items and a moderate amount was found in the verbal items. Vocabulary items favored women if sampled from traditionally female domains but generally not vice versa if sampled from male domains. The sentence completion item format in the English reading comprehension subtest favored men regardless of content. The findings, if supported in a cross-validation study, can potentially lead to changes in how vocabulary items are sampled and in the use of the sentence completion format in English reading comprehension, thereby increasing gender fairness in the examined test.