Lupus anticoagulant is more often associated with thromboembolism than hemorrhage. We have observed two cases of lupus anticoagulant associated with basal ganglion lacunar infarction, causing contralateral choreoathetosis. One patient had no evidence of lupus or other etiology, and responded to antiplatelet therapy, while the other was found to have systemic lupus erythematosus with nephritis and was successfully treated with steroids. The effects of lupus anticoagulant on platelet prostacyclin receptors or prostacyclin production, or its effect on cerebral vessels may permit small-vessel occlusion and lacunar infarction in susceptible patients.