To the Editor: D.P. Devanand, M.D., and colleagues (1) reported that a deficit in identifying odors, as measured by the Pennsylvania Smell Identification Test, predicted later development of Alzheimer’s disease in subjects who were unaware of their olfactory deficit. However, it remains unclear whether the observed deficit was a result of an impairment in olfactory discrimination or of a more general semantic categorization impairment (naming odors or recognizing their names). The few studies of olfactory evoked potentials in Alzheimer’s disease have contradictory results. In the study by Sakuma et al. (2) of patients with Alzheimer’s disease, olfactory evoked potentials had fewer components despite the patients’ having no olfactory dysfunction. By contrast, Hawkes and Shephard (3) found that scores on the Pennsylvania Smell Identification Test were abnormal in eight patients with Alzheimer’s disease, although olfactory evoked potentials were normal in the four who could be tested.