Ataxic hemiparesis is a syndrome in which pyramidal and cerebellar signs occur on the same side. Few authors have suggested that signs or symptoms can orientate toward a supratentorial or toward an infratentorial lesion. We have studied the risk factors and the clinical symptoms of 61 patients consecutively admitted for an ataxic hemiparesis due to a lacunar infarct diagnosed with MRI. The MRI was normal in 2 cases. A tandem lacunar infarct was found in 9 cases (pons and internal capsule in 5 cases, pons and corona radiata in 4 cases) and a clinico-radiological correlation was performed in 50 cases. The comparison of risk factors did not show any difference between the infratentorial (n = 10) and the supratentorial groups (n = 40) excepting for the history of coronary disease. The history of coronary disease was statistically more frequent in the infratentorial group. No difference was found for clinical findings between the 2 groups.