We describe a 62-year-old female diagnosed with Alzheimer's disease, who had been treated with donepezil for approximately 1 year. When she developed a low-grade fever and digestive complaints, her family physician interpreted these symptoms as side effects of the drug and ordered donepezil to be discontinued. Not only was there no improvement of the somatic symptoms after discontinuation of donepezil, but there was also a worsening of the dementia symptoms, culminating in delirium. When donepezil was re-prescribed, the delirium resolved and the patient's mental state stabilized. The authors urge great caution in discontinuing treatment with acetylcholinesterase inhibitors such as donepezil.