Abdominal pain accounts for 5-10% of all emergency department visits in the United States. Some causes of abdominal pain (e.g., acute abdominal aortic aneurysm) are rapidly and irreversibly progressive so that a swift diagnosis is essential for successful therapeutic intervention. The addition of sonography to the evaluation of patients with undifferentiated abdominal pain has been shown to significantly improve the clinician's diagnostic accuracy. This chapter discusses issues and approaches when using ultrasound as an adjunct in the evaluation of patients presenting with acute abdominal pain. Point-of-care sonography is an efficient way to focus the evaluation, including the choice of alternative imaging tests. If there is acute abdominal pain after colonoscopy and biopsy, the sonographer should check for free intra-abdominal air, and so forth. Effective use of point-of-care ultrasound requires proficiency in image acquisition, image interpretation, and integration of the sonographic data into clinical decision-making.