A new approach to assessing unexpected differential item performance (item bias or item fairness) is introduced and applied to the item responses of different subpopulations of Scholastic Aptitude Test (SAT) takers. The essential features of the standardization approach are described. The primary goal of the standardization approach is to control for differences in subpopulation ability before making comparisons between subpopulation performance on test items. By so doing, it removes the contaminating effects of ability differences from the assessment of item fairness. The approach is capable of identifying rare individual instances (outliers) of unexpected differential item performance (that can sometimes be attributed to unfair content), as well as differences on groups of items which might be attributed to the fact that these items are measuring different attributes in different subpopulations. (Author)