Data from the National Longitudinal Study of the High School Class of 1972 were used in a study to investigate the relative effectiveness of high school grades and standardized aptitude test scores, together with demographic characteristics, in predicting early postsecondary educational activity of high school seniors. Self concept and locus of control were also included to determine whether improved prediction would result. Demographic characteristics included sex, race, and socioeconomic status. Students' postsecondary activity was classified as: (1) those enrolled in college; (2) those never enrolled in postsecondary education; (3) those enrolled in postsecondary education but not in college; and (4) those not participating in any educational activity. Membership in one of the groups was used as the criterion in several multiple discriminant analyses, performed with different subsets of the cognitive, noncognitive, and demographic variables. Results indicated that aptitude was the best single predictor of early postsecondary activity. When an individual's aptitude was unknown, grade point average was the next best single predictor. Aptitude and grade point average together were the best combination of predictors. Race, without aptitude results, was not a predictor, and neither self concept nor locus of control were effective predictors. (MH)