Delirium is a frequent cause of hospitalization in the elderly patient, and can be sustained by several factors, which are not always evident. In 1990 Blackburn and Dunn described a clinical picture characterized by the presence of acute urinary retention presenting as delirium, and named it "cystocerebral syndrome". In 1991 Liem and Carter advanced a possible pathophysiological explanation for this phenomenon, suggesting that adrenergic tension might increase in the central nervous system when micturition cannot occur at the usual threshold. The consequent increase in catecholamines level might produce delirium. We report the case of a very old subject with delirium and acute urinary retention, suggestive of the "cystocerebral syndrome", in order to call the attention of geriatricians to acute urinary retention as a possible precipitating factor of delirium.