This chapter examines findings from the newly developed technology of genome-wide association studies (GWAS) being applied to the investigation of Alzheimer disease (AD), primarily in the United States, United Kingdom, and France. These linked research projects make use of many thousands of DNA samples procured from individuals diagnosed with AD, which are then assessed using high-speed throughput technology and compared with control samples, in an attempt to find out what combinations of genes put individuals at increased risk. To date, these enormously expensive projects have provided few if any startling new insights, and many researchers are highly skeptical as to their value. However, others believe that GWAS is a first step toward a more sophisticated way of understanding the interrelated pathways of the numerous genes that appear to be implicated in AD.