The Cancer Prevention Studies (CPS) aim to understand why and how certain people develop cancer while others remain cancer free. In 1959, the CPS-I cohort was established and included approximately 1 million people recruited by 68,000 American Cancer Society (ACS) volunteers in 25 states of the United States of America. Each volunteer was asked to recruit about 10 households with at least one person older than 45 years of age. All household members older than 30 years were asked to complete a questionnaire. Participants were followed annually for mortality data until 1972.