Normal persons show better recognition memory for rare than for common words. In the first experiment, we examined this word frequency effect in 17 patients with dementia of the Alzheimer type (DAT) and 20 normal controls of equivalent age and education. The DAT patients showed a normal tendency to false alarm to common words but failed to show the normal rare word advantage in their hit rate. In a second experiment, we examined normal memory immediately and after a delay of 1 week when it is approximately equivalent to that of DAT patients. There was no attenuation of the usual rare word advantage. These findings suggest that DAT patients fail to encode the featural and intrastructural elements of to-be-remembered verbal information and that this processing deficit may contribute to their impaired recognition memory performance.