Acute abdominal pain is a common presentation in the outpatient setting and can represent conditions ranging from benign to life-threatening. If the patient history, physical examination, and laboratory testing do not identify an underlying cause of pain and if serious pathology remains a clinical concern, diagnostic imaging is indicated. The American College of Radiology has developed clinical guidelines, the Appropriateness Criteria, based on the location of abdominal pain to help physicians choose the most appropriate imaging study. Ultrasonography is the initial imaging test of choice for patients presenting with right upper quadrant pain. Computed tomography (CT) is recommended for evaluating right or left lower quadrant pain. Conventional radiography has limited diagnostic value in the assessment of most patients with abdominal pain. The widespread use of CT raises concerns about patient exposure to ionizing radiation. Strategies to reduce exposure are currently being studied, such as using ultrasonography as an initial study for suspected appendicitis before obtaining CT and using low-dose CT rather than standard-dose CT. Magnetic resonance imaging is another emerging technique for the evaluation of abdominal pain that avoids ionizing radiation.