Ectopic pregnancy occurs when a fertilized ovum implants outside of the uterine cavity. In the United States, the estimated prevalence of ectopic pregnancy is 1% to 2%, and ruptured ectopic pregnancy accounts for 2.7% of pregnancy-related deaths. Risk factors include a history of pelvic inflammatory disease, cigarette smoking, fallopian tube surgery, previous ectopic pregnancy, and infertility. Ectopic pregnancy should be considered in any patient presenting early in pregnancy with vaginal bleeding or lower abdominal pain in whom intrauterine pregnancy has not yet been established. The definitive diagnosis of ectopic pregnancy can be made with ultrasound visualization of a yolk sac and/or embryo in the adnexa. However, most ectopic pregnancies do not reach this stage. More often, patient symptoms combined with serial ultrasonography and trends in beta human chorionic gonadotropin levels are used to make the diagnosis. Pregnancy of unknown location refers to a transient state in which a pregnancy test is positive but ultrasonography shows neither intrauterine nor ectopic pregnancy. Serial beta human chorionic gonadotropin levels, serial ultrasonography, and, at times, uterine aspiration can be used to arrive at a definitive diagnosis. Treatment of diagnosed ectopic pregnancy includes medical management with intramuscular methotrexate, surgical management via salpingostomy or salpingectomy, and, in rare cases, expectant management. A patient with diagnosed ectopic pregnancy should be immediately transferred for surgery if she has peritoneal signs or hemodynamic instability, if the initial beta human chorionic gonadotropin level is high, if fetal cardiac activity is detected outside of the uterus on ultrasonography, or if there is a contraindication to medical management.