A recurrent trend in higher education research has been to identify additional predictors of college success beyond the traditional measures of high school grade point average (HSGPA) and standardized test scores, given that a large percentage of unaccounted variance in college performance remains. A recent study by Wyatt, Wiley, Camara, and Proestler (2012) expanded the definition of college readiness beyond test scores and HSGPA to include a measure of the academic rigor or challenge associated with a student's course work in high school, referred to as the academic rigor index (ARI). This study represents the first examination of the validity of ARI in predicting first-year grade point average (FYGPA). The correlation between ARI and FYGPA indicated a moderate effect overall and by gender, ethnicity, and household income subgroups; however, ARI did not add incremental validity above SAT scores and HSGPA. Additionally, when added to SAT scores and HSGPA, ARI had no impact on differential prediction by relevant subgroups. Given the current movement toward a more holistic assessment of college applicants, a standardized measure of the academic rigor of a student's course load in high school suggests a promising additional measure to the assessment of a student's level of college readiness. Table A-1 is appended.