AFTER THE phenomenally high incidence of amyotrophic lateral sclerosis among the Chamorros of Guam was noted, an effort was made to identify other neurologic disorders in the inhabitants of this island.11 It soon became evident that the Chamorros also had a high incidence of a form of parkinsonism with dementia2 which may be unique to this population. A surveillance program was developed to assess the incidence and prevalence of other neurologic and myopathic disorders and to determine whether any might be associated with amyotrophic lateral sclerosis or parkinsonismdementia. To this end, we analyzed case reports in a fashion similar to that in an earlier epidemiologic study in a population of similar size in Rochester, Minn.3 A second paper will provide a genetic analysis of several familial disorders which have been observed among the Chamorros. Since 1956 the National Institute of Neurological Diseases and Blindness