PURPOSE: To compare the usefulness of fluid-attenuated inversion recovery (FLAIR) MR imaging with that of unenhanced CT in the detection of acute intraventricular hemorrhage (IVH). MATERIALS AND METHODS: Thirty-four patients with acute IVH underwent FLAIR MR imaging and unenhanced CT within three days of the onset of symptoms. Except in one patient, all MR studies were performed after CT. The mean time intervals between CT and symptom onset and between CT and MR examinations were six and five hours, respectively. Two radiologists evaluated the detectability and conspicuity of acute IVH at FLAIR MR imaging and unenhanced CT. Positive imaging criteria in the detection of acute IVH were intraventricular hyperintensity at FLAIR MRI and hyperattenuation at CT. RESULTS: Acute IVH was detected in all patients at FLAIR MR imaging and in 30 (88%) of 34 patients at unenhanced CT. In 32 patients (94%), the conspicuity of IVH at FLAIR MR imaging was as good as or better than that at unenhanced CT. CONCLUSION: FLAIR MR imaging was superior to unenhanced CT in the detection of acute IVH.