Around the world, women use oral contraceptive pills for contraceptive as well as many non-contraceptive benefits. Concerns regarding the risks associated with use of hormonal contraceptives have existed since introduction of the first products. Early on, investigators identified the risk of venous thromboembolism (VTE) and attributed this to the estrogen component of the pill as a dose-dependent effect. Although combined hormonal contraception increases the risk of VTE events, the absolute risk remains low, and the same underlying identifiable risk factors exacerbate the risk of thrombosis in both users and nonusers. Over the years, we have seen changes to pill dosing and formulation, including the introduction of new progestins. This has given rise to new questions and concerns regarding risks of specific pills. At the same time, we have improved diagnosis of VTE and gained further insights regarding baseline risk factors, and changes have occurred in both population health and the available options for birth control. Clinical questions and controversies have emerged including risks of progestogens, if screening is indicated, and how to provide patient-centered counseling. This chapter will: Review the action of combined hormonal contraception.Provide an understanding of estrogens and progestogens used for contraception.Discuss the risk of venous and arterial embolic events, risk factors, and how hormonal contraception modifies these risks.Guide interpretation of the evidence regarding risks of combined hormonal contraception.