Pelvic inflammatory disease is a polymicrobial infection of the upper genital tract. It primarily affects young, sexually active women. The diagnosis is made clinically; no single test or study is sensitive or specific enough for a definitive diagnosis. Pelvic inflammatory disease should be suspected in at-risk patients who present with pelvic or lower abdominal pain with no identified etiology, and who have cervical motion, uterine, or adnexal tenderness. Chlamydia trachomatis and Neisseria gonorrhoeae are the most commonly implicated microorganisms; however, other microorganisms may be involved. The spectrum of disease ranges from asymptomatic to life-threatening tubo-ovarian abscess. Patients should be treated empirically, even if they present with few symptoms. Most women can be treated successfully as outpatients with a single dose of a parenteral cephalosporin plus oral doxycycline, with or without oral metronidazole. Delay in treatment may lead to major sequelae, including chronic pelvic pain, ectopic pregnancy, and infertility. Hospitalization and parenteral treatment are recommended if the patient is pregnant, has human immunodeficiency virus infection, does not respond to oral medication, or is severely ill. Strategies for preventing pelvic inflammatory disease include routine screening for chlamydia and patient education.