PURPOSE: To determine the nature of large deep -seated infarcts without cortical infarct in patients withsteno-occlusive disease of the proximal middle cerebral artery(MCA) using magnetic resonance images(MRI) andangiography. MATERIALS AND METHODS: By means of MRI and MR angiography(MRA), we examined 24 patients with largedeep cerebral infarctions(>3cm in size) involving the basal ganglia, corona radiata and/or centrum semiovale, aswell as steno-occlusive lesion of the proximal MCA. According to location, infarctions were classified into fivegroups, as follows: Group 1: basal ganlgia and corona radiata; 2: basal ganglia, corona radiata and centrumsemiovale; 3: corona radiata and centrum semiovale; 4: corona radiata; 5: basal ganglia only. We evaluated thetopography of the lesions and correlated the results with the findings of angiography(all 24 MRA; the 13:conventional angiography). Involvement of the head of the caudate nucleus and the internal capsule were alsoevaluated. RESULTS: Fifteen of 24 cases(63%) were assigned to group 1 (4 proximal MCA(M1) occlusion and 11stenosis), and five of 24 (21%) with M1 occlusions to group 2. Group 3 comprised only one case with M1 occlusion.Two cases with both occlusion and stenosis were included in group 4, and only one case-with M1 stenosis-in group5. Infarctions at the caudate nucleus were seen in five cases, and at the internal capsule in two. On conventionalangiography(13 cases) cortical branches of the MCA were delineated through the leptomeningeal collaterals ofanterior or posterior cerebral arteries. CONCLUSION: Most large deep cerebral infarctions found in proximal MCAdiseases are thought to extend cephalad to the corona radiata. When large deep-seated infarctions with proximalMCA occlusion is observed more frequently than stenosis.