This study examined the separate and joint use of high school course grades, course work taken, and American College Testing Program (ACT) Assessment subject area scores for making course placement decisions. The data for this study were obtained from nine institutions through their participation in a pilot study of the ACT Course Placement Service. College courses included were remedial and standard mathematics courses, reading courses, and English courses. Sample sizes ranged from 26 to 2,109, but typical sample sizes exceeded 100 students for all courses. For standard-level courses, the ACT Assessment subject area score, the high school subject area average, and the overall high school average were all effective for making accurate placement decisions, but the ACT Assessment score was the most effective. Using either the ACT Assessment score and the high school subject area average jointly, or the ACT Assessment score and overall high school average jointly improved the accuracy of placement decisions over that obtained with a single predictor. The number of high school courses taken in a particular subject area was the least effective variable for making placement decisions for standard-level courses. (Contains 5 references and 12 tables.) (Author/SLD)