As the role of the general surgeon continues to evolve, the surgeon's use of ultrasound will surely influence practice patterns, particularly for the evaluation of patients in the acute setting. With the use of real-time imaging, the surgeon receives "instantaneous" information to augment the physical examination, narrow the differential diagnosis, or initiate an intervention. With select ultrasound examinations, the surgeon can rapidly evaluate adult and pediatric patients who present with an acute abdomen, especially those in shock. In the hands of the surgeon, this noninvasive bedside tool can more accurately assess the presence, depth, and extent of an abscess, confirm complete aspiration, or diagnose wound dehiscence before it is apparent on physical examination. Ultrasound is so accurate for the diagnosis of pyloric stenosis that it has essentially replaced the upper gastrointestinal series in most institutions. The surgeon's use of ultrasound to detect a pleural effusion has virtually replaced the lateral decubitus film. Furthermore, an ultrasound-guided thoracentesis not only facilitates the procedure but improves its safety. Many ICUs now have protocols in place to perform routine duplex surveillance of those patients who are considered at high risk for the development of thromboembolic complications. As surgeons become more facile with ultrasound, it is anticipated that other uses will develop to further enhance its value for the assessment of patients in the acute setting.