Over 60 million women around the world are now using oral contraceptives because it is very effective, easy to use, and safe for most women. Defined as containing less than 50 micrograms of estrogen, low-dose pills account for over 85% of pills sold in developed countries, almost 60% of pills sold in developing countries, and almost 80% of pills supplied by donor agencies. Lower-dose pills seem to cause fewer unpleasant side effects, such as nausea or dizziness. Research over 3 decades shows that the pill has noncontraceptive benefits and risks. It helps to prevent 2 major types of cancer--endometrial cancer and epithelial ovarian cancer. It also helps to prevent anemia, ectopic pregnancy, painful menstruation, certain benign breast tumors, and ovarian cysts. The pill increases the risk of certain circulatory system diseases, mainly thromboembolism but also stroke and heart disease, for some women, although this risk has been seen mainly in older women who smoked and used higher-dose pills. Little research on these issues have involved low-dose pills, which makes interpretation for today's pill users difficult. The biggest benefit of the pill is its effectiveness. Recent studies of breast cancer have produced confusing results. Concern is focused on women who took the pill while they were young or before having their 1st child. A plausible hypothesis now emerging is that the pill may accelerate breast cancer development in these women. While not every question is answered about the pill, it remains the method that many young women want for spacing their pregnancies.