The major benefits of modern low-dose oral contraceptives include relative safety and a high degree of efficacy, decreasing the need for abortion or surgical sterilization; reduced risks of bacterial (but not viral) pelvic inflammatory disease and of endometrial and ovarian cancer; improved menstrual regularity, with less dysmenorrhea and blood flow; and, when low-dose combination (not progestogen-only) oral contraceptives are used, reduced acne and hirsutism. Major risks are cardiovascular. Preliminary data from nonrandomized studies suggest that oral contraceptives containing third-generation progestogens are associated with increased risk of venous thromboembolism, particularly in carriers of the coagulation factor V Leiden mutation. The risk of arterial thrombosis, such as myocardial infarction or stroke, may be directly related to estrogen dose, particularly in women who have hypertension, smoke, or are >35 years old. Considering that only users aged >/=30 years who smoke >/=25 cigarettes/d have a higher estimated mortality rate than that of pregnant women, the benefits of oral contraceptives appear to outweigh their risks.