A 76-year old white married female had rapid onset dementia with myoclonus and was admitted to an HMO hospital where she was initially diagnosed as Alzheimer's disease. The physician-husband suggested that the condition might be due to the Pepto-Bismol which she had taken chronically to control her irritable bowel syndrome. An elevated serum bismuth level of 242 μg/L (normal is 5 μg/L) established bismuth toxicity as the cause of the dementia. With treatment the patient returned to a normal mental state. The possibility of bismuth encephalopathy needs to be considered in the differential diagnosis of possible Alzheimer's dementia.