Sonographic evaluation of the pregnant patient suspected of harboring an ectopic pregnancy (EP) helps determine patient management. Although clinicians typically ask sonologists to "rule out" EP in these patients, the sonologist actually must answer 3 questions: (1) Is there an intrauterine pregnancy (IUP)? (2) Is the possibility of normally developing IUP reliably excluded? (3) Are there sonographic findings that identify or increase the likelihood of an EP? Understanding the rationale behind these questions and the sonographic findings that help to answer these questions enables the sonologist to contribute meaningfully to the care of patients with possible EP. Beginning the sonographic examination with a limited transabdominal approach has value. An IUP can be confidently diagnosed by identification of an intradecidual sac exhibiting the double decidual sac sign, yolk sac, or embryo. When the serum β human chorionic gonadothropin exceeds 2000 mIU/mL, a technically excellent sonographic examination should identify an intradecidual sac potentially representing an IUP. Even without directly visualizing a yolk sac or embryo in the adnexa, the presence of an extraovarian mass or hemoperitoneum strongly predicts the possibility of EP. An intraovarian mass with peripheral hypervascularity is more likely to represent the corpus luteum rather than an intraovarian EP. Cervical EP can be distinguished from the cervical phase of a spontaneous abortion in progress by either demonstrating fetal heart motion or persistence or enlargement of findings on short-interval follow-up. Absence of a myometrial mantle surrounding one edge of an IUP positioned at the fundus is suspicious for an interstitial EP.