Fiberoptic instruments have improved the accuracy of diagnosis of lesions of the upper digestive tract, particularly since the capability to perform biopsy under direct vision has been developed. Primary rhabdomyosarcoma of the upper gastrointestinal tract is an extremely rare entity. A literature search has revealed only 10 instances of rhabdomyosarcoma involving the esophagus, stomach, or duodenum (1-5). In this report, we describe the use of fiberoptic diagnosis and gastroduodenoscopic biopsy in a patient with rhabdomyosarcoma of the stomach and duodenum.