The Oxford–FPA Contraceptive Study is a long-term cohort study designed to investigate the relationship between oral contraceptive use and cancer incidence, involving 17,032 women recruited from contraceptive clinics in England and Scotland. Between 1968 and 1974, participants were enrolled in-person at clinics while using oral contraceptives, diaphragms, or intrauterine devices. The cohort consisted of married women aged 25 to 39 years, who were white British. Participants were followed for over four decades, with cancer incidence monitored continuously through health records and registries until the study concluded in 2010.