I commend Weissenborn et al.(1) for careful serial neurologic and neuropsychological examination of 42 severely ill adults. I question whether encephalopathy or delirium is the best description. The first of 2 cardinal features of delirium on the Confusion Assessment Method (CAM)(2) is acute confusion with fluctuating course. All the observations support sudden onset. The low median age of 43 years makes prior brain disease such as Alzheimer disease and stroke unlikely in most subjects. Figure 2 demonstrates great fluctuation in neuropsychological dysfunction.(1) The second CAM cardinal feature is inattention. Twenty-one patients had impaired working memory. We can safely infer that almost all 21 had inattention; 10 patients with stupor or coma had inattention. Thus the first 2 cardinal features of delirium were fulfilled in an estimated 30 patients. CAM positivity requires disorganized thinking or altered level of consciousness. Ten had altered level of consciousness and many of the 24 patients whose Mini-Mental State Examination fell below 28 or the 5 who developed agitation would likely have disorganized thinking. I estimate 50% of these patients had CAM-positive delirium. In 584 key articles on delirium, this is the first report of delirium in adults with hemolytic uremic syndrome.