Data from Project Talent and the National Longitudinal Study of the High School Class of 1972 provided comparable data on changes between 1960 to 1972 in reading ability and other characteristics of high school seniors, college entrants, and Scholastic Aptitude Test (SAT) takers. Each group showed a decline in reading ability, but the drop for SAT takers was greater than that for the other two groups. A much greater increase in the proportion of low ability than of high ability students taking the SAT appeared to be the predominant source of the score decline. The decrease in ability level of high school seniors also contributed to the decline. There were appreciable changes in the background characteristics of all groups in terms of age, sex, parental educational and occupational background, family configuration, high school curriculum, and expected college major. However, none of these factors provided a major explanation of the decline among high school seniors and college entrants. A decrease in the percentage of SAT takers entering four-year colleges might help explain the greater decline observed for this group. Some evidence indicated that SAT scores earned in 1960 and 1972 are not precisely comparable; thus, the actual decline was somewhat greater than the SAT scores indicated. (Author/EVH)