Twenty-two patients with clinical signs and symptoms compatible with lacunar transient ischemic attack or stroke of varying chronicity were evaluated with MR imaging. CT was also performed in 21 of these patients. MR revealed small, deep cerebral lesions in locations appropriate to the clinical symptoms in 19 patients. Lacunar infarcts were imaged by CT in 11 patients; however, no lesions were identified on CT that were not detected with MR. Presumed lacunar infarcts were identified on MR images in 17 additional patients. Lacunae generally appeared as focal areas of decreased signal intensity on T1-weighted images and as focal areas of increased signal intensity on T2-weighted images. T2-weighted MR images detected a greater number of lacunar infarcts than did mixed T1-/T2-weighted images, which in turn detected more lacunae than did T1-weighted images. In general, acute lacunar infarcts (within 1 week of onset or recurrence of clinical symptoms) were seen only on T2-weighted images, while chronic lesions (more than 1 week) were seen on both T1- and T2-weighted images. Our results indicate that MR is superior to CT for evaluating lacunar infarcts, and second, that T2-weighted images are more sensitive than T1- and mixed T1-/T2-weighted images for detecting lacunar infarcts.