Many epidemiological studies of Alzheimer's disease (AD) have been conducted. This review discusses the most recent findings in relation to the possibilities of prevention of this disease. Data on the diagnostic validity are also reported. The primary prevention of AD is hampered by limitations in the knowledge and understanding about its risk factors. Among the factors that have been investigated, only age, familial aggregation, and apolipoprotein E gene‐e4 allele are definite risk factors both for early‐ and late‐onset AD. However, many of the possible and putative risk factors, if definitely confirmed, can be prevented or controlled. Secondary prevention is not currently practicable as valid predictive tests and efficacious treatment are lacking. In contrast, much data is available to support tertiary prevention interventions, such as better planned patient