The relationship was investigated between test scores obtained from the Iowa Tests of Basic Skills (ITBS) and the Iowa Tests of Educational Development (ITED), and the grade point average (GPA) at the high school and college level. The data used were unique in providing a longitudinal comparison of college students' performance with the results of their early elementary achievement test performance. Specifically, the predictive validity of the ITBS and the ITED was investigated. Records of 1,997 graduates of Iowa high schools who entered the University of Iowa as freshmen in the fall of 1977 were analyzed. Zero-order correlations were computed between ITBS composite scores (grades 4, 6, and 8) and: (1) four-year high school GPA; (2) high school percentile rank; and (3) first semester freshman college GPA. Similar correlations were computed using ITED composite scores (grades 9-12) in place of ITBS scores. Separate correlations were also computed for males and females. Results supported the contention that proficiency in basic skills at the elementary and high school levels, as measured by ITBS and ITED, does have a significant relationship to high school and college academic success for both males and females. (RL)