Mortality resulting from cancer is generally lower in AFF populations than in the overall American population (Hanrahan et al., 1996). That may be due in part to greater use of preventive measures and clinical screening in some AFF worker populations than in other working populations. It could also be due to the protective effect of some AFF exposures—a phenomenon that deserves further exploration (NIOSH, 2007c). The higher incidence of primary intracranial glioma among male farmers compared to the general population led to the design and implementation of a case-control study conducted jointly by NIOSH and two extramurally funded Ag Centers (Great Plains Center for Agricultural Health in Iowa and the National Farm Medicine Center in Wisconsin). Results of the effort are emerging. In general, cancer mortality in American males has declined (American Cancer Society, 2007), so any decline attributed to occupational exposure needs to exceed historically observed declines.