Endoscopic ultrasound (EUS) is an emerging technique that can be used to visualize lesions in or adjacent to the gastrointestinal tract. We performed a review of current indications and capabilities of endoscopic ultrasound. EUS provides diagnostic information on submucosal lesions of the gastrointestinal tract. It is the most accurate method for local staging of esophageal and rectal cancer. It appears to be more sensitive in detecting common bile duct stones than endoscopic retrograde cholangiopancreatography. Furthermore, its use avoids the risk of pancreatitis. Lesions deep to the gastrointestinal tract, such as mediastinal nodes or pancreatic lesions, can be biopsied through the EUS endoscope. New therapeutic uses of EUS include aid in endoscopic drainage of pancreatic pseudocysts and celiac axis neurolysis for the treatment of pain from pancreatic cancer. EUS offers many new diagnostic capabilities to visualize and biopsy lesions in or adjacent to the gastrointestinal tract. Therapeutic uses are also emerging for this new technique.