The Agricultural Health Study (AHS) - Cancer Risks is a prospective study of cancer in a cohort of 89,000 licensed pesticide applicators and their spouses from Iowa and North Carolina. The AHS began in 1993 and continues with ongoing studies with the goal of answering important questions about how agricultural lifestyle and genetic factors affect the risk of cancer among farmers and commercial applicators. The study is a collaborative effort involving investigators from National Cancer Institute, the National Institute of Environmental Health Sciences, the Environmental Protection Agency, and the National Institute for Occupational Safety and Health.