This article describes the formulation and execution of the Rainbow Project, Phase I, funded by the College Board. Past data suggest that the SAT is a good predictor of performance in college. But in terms of the amount of variance explained by the SAT, there is room for improvement, as there would be for virtually any single test battery. Phase I of the Rainbow Project, described here, uses Sternberg's triarchic theory of successful intelligence as a basis to provide a supplementary assessment of analytical skills, as well as tests of practical and creative skills, to augment the SAT in predicting college performance. This assessment is delivered through a modification of the Sternberg Triarchic Abilities Test (STAT) and the development of new assessment devices. Results from Phase I of the Rainbow Project support the construct validity of the theory of successful intelligence and suggest its potential for use in college admissions as an enhancement to the SAT. In particular, the results indicated that the triarchically based Rainbow measures enhanced predictive validity for college GPA relative to high school grade point average (GPA) and the SAT and also reduced ethnic group differences. The data suggest that measures such as these potentially could increase diversity and equity in the admissions process.