© 2017 RSNA. To determine the prevalence of the spot sign and the accuracy of using the spot sign to predict intracerebral hemorrhage (ICH) expansion with standardized multiphase computed tomographic (CT) angiography. Materials and Methods: This prospective observational cohort study included 123 consecutive patients with acute ICH (onset ,6 hours). Patients underwent multiphase CT angiography in three automated phases after injection of contrast material. Patients were classified as having one of four patterns (pattern A, B, C, or D) according to the presence of the spot sign in the three phases. Pattern A was the more arterial pattern, and pattern D was the more venous pattern. Ninety-five patients underwent follow-up unenhanced CT 24 hours after symptom onset. Primary outcome was substantial hematoma expansion (.33% or .6 mL) at 24 hours. Associations between the presence of the spot sign and substantial hematoma expansion were assessed by using the Pearson x2 test. Results: The later the phase of CT angiography, the higher the frequency of the spot sign. The spot sign was seen in 29.3% of patients in phase 1, 43.1% of patients in phase 2, and 46.3% of patients in phase 3 (P<.001). The presence of the spot sign in any phase was related to substantial hematoma expansion (P<.001 for all comparisons; Bonferroni adjusted α= .0125), with highest positive predictive value in phase 1 (64.0%) and highest negative predictive value in phase 2 (90.2%). The more arterial the pattern of spot sign presentation, the greater the frequency of substantial hematoma expansion (P = .013). Absolute hematoma growth analysis revealed a hierarchical pattern of spot sign presentations, as follows: A>B>C>D>no spot sign (P = .002). Conclusion: Multiphase CT angiography can help differentiate among different forms of spot sign presentation and can help stratify patients at risk for hematoma expansion. The more arterial the spot sign pattern, the greater the frequency and extent of expansion.