This study is a randomized, double-blinded, controlled trial comparing two regimens of doxycycline for the prevention of infection after surgical abortion. One thousand women undergoing surgical abortion in the first trimester will be enrolled from the clinic at Tu Du Hospital, Ho Chi Minh City, Vietnam. The standard regimen has been 100 mg twice daily for 5 days after the abortion. Subjects will be randomized to the standard regimen or to take 200 mg doxycycline pre-operatively. Subjects found to have a positive Chlamydia EIA test will receive a 7-day course of doxycycline regardless of study group. Subjects will complete questionnaires of symptoms, including nausea and emesis in the recovery room after the procedure and at a single follow-up visit two weeks later. The primary outcome will be infection after abortion, defined below. Analyses will be performed including and excluding Chlamydia-positive subjects. Secondary outcomes will be the proportion with nausea, emesis, and other side-effects.