The authors describe a new magnetic resonance (MR) imaging sign of acute cerebral ischemia/infarction. Abnormally contrast material-enhanced curvilinear structures were demonstrated in eight patients in the evolving area of cerebral ischemia/infarction within 26 hours after the ictus on contrast-enhanced, high-field-strength (1.5-T), T1-weighted spin-echo images. The abnormal enhancement is considered to represent cortical arterial vessels of markedly slowed circulation in areas of underlying brain injury, which will eventually progress to frank brain infarction. This was demonstrated at computed tomographic (CT) and follow-up MR examinations. Characteristically, the degree of the contrast enhancement of vessels appeared most intense in the proximal portions, and the intensity of enhancement gradually diminished in the more distal portions of these vessels as they pass over the convexities and finally disappear.