To the Editor.— In the April issue of theArchives(33:217, 1976), two items of interest warrant comment. These pertain to the prevalence and malignancy of Alzheimer disease (AD) reported by Katzman and his associates. We agree that AD is certainly malignant in that its course is relentless and eventually terminates in death. We also agree that in patients with AD who through inanition become vulnerable to intercurrent infections, the primary diagnosis of AD should be made in pathologically proved instances. We believe that the clinical course of AD is so characteristic that if the patients are periodically examined at about six-month intervals, preferably by the same physician, no special "neuropsychological" tests are necessary to establish the clinical diagnosis. It should be borne in mind, however, that the progressive deterioration is quite similar to that of Pick disease and progressive subcortical gliosis, so that definitive diagnosis still must be determined