Differential item functioning (DIF), or item bias, occurs when individuals in a focal group respond differently to a test item than do individuals in a reference group even when comparisons are restricted to individuals with similar overall skill levels on the trait in question. It is common in constructing a questionnaire or survey to recommend that an item analysis be conducted in a manner similar to that used in cognitive measurement, but it is not common to be concerned with items as they perform differently. DIF has apparently not yet been widely recognized as a tool for developing a survey or for understanding survey responses. The Mantel Haenszel procedure is one of the empirical methods most commonly used to identify DIF, and its use in survey development is explored. Two examples, one involving the evaluation of student achievement for 777 male and 773 female elementary school students, and the other involving the evaluation of human service workshops for 798 participants aged over 40 years and 884 who were younger, illustrate the way in which information about DIF could have aided in the development of the instrument and interpretation of the data. DIF detection would seem a useful adjunct to the traditional item analysis that could be of substantial value at the pilot or revision stage of instrument development. (Contains 4 figures and 20 references.) (SLD)