This study will determine if laparoscopy can be used successfully to find and remove insulinomas (insulin-secreting tumors of the pancreas). These tumors are very small and often difficult to locate with magnetic resonance imaging (MRI), computed tomography (CT) or ultrasound. Invasive procedures, such as arteriograms (X-ray imaging using a contrast agent injected into the bloodstream through a catheter) and venous sampling are more successful but involve more patient discomfort and greater risk. This study will test whether laparoscopy can be used to replace some or all of these tests, as well as more extensive surgery.