Cancer prevention is central to the mission of the American Cancer Society (ACS). The ACS's prevention activities take many forms, but are primarily focused on modifiable risk factors that have been demonstrated to have the largest impact on cancer risk in the general population (with particular emphasis on tobacco use because of its large impact on cancer), and well-proven policy and program interventions. The ACS addresses nutrition, physical inactivity and obesity, alcohol consumption, excessive sun exposure, prevention of certain chronic infections, and selected other environmental factors through a variety of venues, including consensus guidelines (eg, nutrition and physical activity, human papillomavirus vaccination) and developing educational materials for health care providers and the general public. In contrast to the broad definition of environmental factors used by the ACS and most other public health agencies, some members of the general public associate the term “environmental” only with toxic air and water pollutants and other, predominantly manmade, hazards that people encounter, often involuntarily, in their daily life. This article will provide an overview of the ACS's approach to the prevention of cancer associated with such toxic pollutants in the context of its mission and priorities with respect to cancer prevention. CA Cancer J Clin 2009. © 2009 American Cancer Society.