Over the past 50 years, there have been hundreds of clinical studies investigating whether hormonal contraception changes the risk of cancer among users. Most of the epidemiological evidence comes from observational case control and cohort studies examining cancer risk among users of combined oral contraceptives (COCs). Although women may be at increased risk of several cancers (breast, cervix, liver and thyroid) whilst using this contraceptive method, the effects appear to be transient, disappearing within a few years of stopping. Conversely, COCs protect against several other cancers (ovary, endometrium and colorectum), with the benefits persisting for many years after stopping. This sustained protection may produce major public health benefits over time, through reduced overall cancer incidence and mortality. Limited data suggests that users of progestogen-only contraceptives (especially injectables and implants) experience a similar pattern of cancer risks and benefits as COC users.