Some reports have suggested that naloxone, a short-acting opiate receptor blocker given intravenously, has a beneficial effect on the symptoms of senile dementia of the Alzheimer type. We have performed a double-blind, crossover trial of naltrexone, an orally active, long acting opiate antagonist, in 17 Alzheimer-type dementia patients. None showed any improvement in assessments of day-to-day living skills or on a battery of neuropsychological tests. No side effects were noted. In the dosage used, naltrexone appears not to be useful in Alzheimer-type dementia.