Two editions of the Verbal and Mathematical portions of the Scholastic Aptitude Test (SAT) were used to study differential speededness and differential omission and the relationships among differential item functioning (DIF), differential omission, and item difficulty for Asian Americans, Blacks, Hispanics, and females in a total sample exceeding 300,000 SAT examinees in 1984 and 1985. Consistent and replicable evidence of differential speededness was found for Blacks and Hispanics. Use of an unspeeded criterion for matching in place of the traditional total score, which contains speeded items, did not affect the DIF analyses of speeded items. A strong artifactual negative relationship between DIF and differential omission was found. The relationship between differential omission and difficulty was consistently positive on the Verbal sections for all comparison groups except the Asian-American group, for whom it was consistently negative. On the mathematical sections, this relationship was consistently found for the female/male comparison, for whom it was negative. Finally, the relationship between difficulty and DIF was negative but smaller than previously observed. (Contains 8 tables, 8 figures, and 31 references.) (Author/SLD)