Endosonography (EUS) is a relative newcomer to the field of gastrointestinal endoscopy. Nevertheless, two prospective studies with similar results have shown that EUS leads to a change in management in roughly two-thirds of patients in whom it is performed, with many of these changes being to less invasive or less expensive management. Preliminary investigations on the use of catheter probes for performing EUS have shown similar effects. Specific investigations on the effect of EUS on the outcomes of patients with submucosal tumors, esophageal cancers, pancreatic cancers, and rectal cancers need to be performed. Selective studies have demonstrated EUS to be cost-effective for the management of submucosal tumors and ampullary tumors. The complication rate of EUS appears to be comparable to that of upper endoscopy. There is little or no information regarding training in EUS, practice variation, or affect of EUS on quality of life.