Background and Purpose-Intracerebral hematomas (ICHs) often increase in size in the initial hours. It is unknown whether expansion of ICHs after aneurysmal rupture in the acute phase is always a sign of rerupture of the original aneurysm. Methods-We included patients with an ICH from a ruptured aneurysm who underwent computed tomography imaging within 24 hours of symptom onset and a repeat computed tomography within 48 hours. Hematoma growth was considered present when there was a 33% increase in hematoma volume, as assessed by the ABC/2 method. Clinical and radiologic characteristics were compared between patients with ICH growth, with and without clinical signs of rerupture. Rerupture was defined as a sudden deterioration in the level of consciousness in the absence of ventricular enlargement or a systemic cause. Results-Hematoma expansion within 48 hours after onset occurred in 12 of the 49 included patients and was preceded by clinical evidence of rerupture in 6 of these 12 patients. Of the 6 patients without an evident rerupture, 3 had no clinical deterioration, 1 had respiratory failure due to pneumonia, another had temporal brain herniation, and the last had acute hydrocephalus. Conclusion-Only half of the patients with early ICH expansion after aneurysmal rupture had clinical signs of rerupture of the aneurysm. Early ICH expansion after aneurysmal rupture can be caused by other mechanisms, which are possibly comparable to those responsible for hematoma expansion in spontaneous ICH. (Stroke. 2010;41:2592-2595.)