BACKGROUND: Current US guidelines recommend the Asthma Control Test (ACT) for assessing disease control and selecting treatment. OBJECTIVE: The goal of this study was to prospectively assess the ACT and its component questions for their utility in predicting the risk of severe asthma exacerbations. METHODS: Individuals were participants in the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-Ethnicity, and those included in the current analysis had the following characteristics: age 18 years or more, physician-diagnosed asthma, and longitudinal care received at a large health system in southeastern Michigan. Study participants underwent a baseline evaluation, which included answering the ACT. A severe asthma exacerbation was defined as one requiring oral steroids, an emergency department visit, or inpatient admission. Receiver-operator characteristic curves were used to measure and compare the predictive utility of the ACT and its component questions for severe asthma exacerbations. RESULTS: Of 1180 participants, 354 (30.0%) experienced a severe asthma exacerbation within 6 months of their baseline evaluation. When compared with the individual questions that composed the ACT, the composite score was significantly better at predicting severe exacerbations with 1 exception; the composite ACT score and the question assessing rescue medication use were not significantly different (P = .580). Pharmacy-based records of metered-dose inhaler short-acting beta-agonist use and asthma severity were also not significantly different from the composite ACT score. CONCLUSIONS: Our study demonstrates that although the ACT is modestly predictive for exacerbations, the composite score may not be superior to assessing rescue medication use alone for predicting the risk of severe asthma exacerbations.