Pelvic inflammatory disease (PID) is an infection of the endometrium, fallopian tubes, and adnexae caused by a wide variety of bacteria, including Chlamydia trachomatis, Neisseria gonorrhoeae, and genital tract bacteria, most notably anaerobes. PID is often asymptomatic but clinical manifestations can range from mild pelvic pain and tenderness to severe peritonitis. Pelvic abscess formation is a serious infectious complication. However, only about 5% of patients with PID have a fever or severe infectious manifestations. An accurate clinical diagnosis of PID is difficult and it is commonly confused with other pelvic conditions, including ectopic pregnancy, appendicitis, and rupture or torsion of an ovarian cyst. Antibiotic therapy is aimed primarily at C. trachomatis, N. gonorrhoeae, and anaerobic bacteria, with prompt identification and treatment of PID recommended in an attempt to reduce the 15% rate of tubal infertility and 40% risk of chronic pelvic pain following this infection.