Six patients completed a two-year double-blind, placebo-controlled crossover design study of the effects of sodium fluoride on the course of Alzheimer's disease (AD). Patients were screened and only those meeting DSM lll criteria for Primary Degenerative Dementia (senile or presenile onset) were entered into the study. Other inclusion/exclusion criteria are described in an accompanying publication. Patients were given a battery of cognitive, speech, and memory tests every three months while taking either 90 mg of sodium fluoride q hs (in controlled-release capsules) or placebo capsules similar in appearance. The rationale for this pilot study is based on the aluminum hypothesis of AD.