The differential item functioning of mathematics performance of Hispanic, Asian, and White students on the National Assessment of Educational Progress (NAEP) was studied, using a modification of the Mantel-Haenszel Procedure. The sample for grades 3, 7, and 11, respectively, included: (1) 1,367, 1,570, and 1,580 Whites; (2) 265, 613, and 760 Asians; (3) 1,238, 1,602, and 1,022 Mexican Americans; (4) 566, 624, and 458 Puerto Ricans; and (5) 292, 347, and 566 Cubans. The data are from the 1985-86 NAEP regular assessment and the NAEP special supplemental study of language minority students. With the exception of third graders, no simple explanation could be offered as to why some items were more difficult or easier for ethnic group members. For the third grade, items with little or no text, involving simple arithmetical operations, were differentially easier for many ethnic group members. Overall, as many items favored the language groups as favored the majority comparison group at each grade level. Four tables summarize the study data. (SLD)