The diagnosis of acute mental status changes in the elderly patient is often very difficult. Many causes are possible, and there is often little history obtainable. The physical examination occasionally provides the essential clues needed to discover the source of the sudden deterioration. We have recently evaluated four episodes of acute delirium in three elderly patients who presented with no readily apparent cause for these changes. On further evaluation, the patients were found to have marked bladder distention associated with acute urinary retention. None of these patients complained of discomfort, and none had any awareness or recollection of their deterioration. Each patient had rapid resolution of symptoms on bladder decompression. To our knowledge, this "cystocerebral syndrome" has not been previously described, and we suggest that it be considered in the evaluation of acute confusional states in elderly men.