This study examined the effects of using ACT Composite scores and high school averages in making college admission decisions for students from selected racial/ethnic groups. The analyses were based on 2 samples: an African American/Caucasian sample of 262,553 students from 43 postsecondary institutions and a Hispanic/Caucasian American sample of 174,890 students from 25 institutions. In addition, the effect of adding other variables on the access rates of African American and Hispanic students was studied. African American and Hispanic students with a given high school average typically had a much lower probability of success than did Caucasian students with the same high school average. The corresponding differences in the probability of success, given ACT Composite score, were similar in direction but smaller in magnitude. This, total-group predictions based on either high school average or ACT Composite score were found to overestimate the first-year performance of African American and Hispanic students relative to that of Caucasian American students. ACT scores and high school averages were slightly more accurate for predicting first-year success of African American students than of Caucasian American students. The opposite result was true for Hispanic students. Moreover, smaller percentages of African American and Hispanic students than Caucasian American students achieve benchmark values of high school average, ACT Composite score, or a predictive index based on ACT Composite score and high school average jointly. (Contains 7 tables, 4 figures, and 32 references.) (Author/SLD)