Gastrointestinal stromal tumor is a common type of gastrointestinal mesenchymal tumor. Depending on the patient's age, compliance and health status, and the level of suspicion of malignancy, tumors ≤3 cm in size are typically monitored annually by endoscopic ultrasonography. The examination interval can be extended if no size change is noted on consecutive examinations. We report here on a 44-year-old female who presented with abdominal discomfort and displayed no size change of her gastrointestinal stromal tumor on three consecutive endoscopies over a 44- month interval. The patient was diagnosed with malignant gastrointestinal stromal tumor on the basis of the evident ulceration seen on esophagogastroduodenoscopy and the inhomogenous echo noted on the endoscopic ultrasonography and the pathologic findings by gastric wedge resection. (Korean J Gastrointest Endosc 2010;41:21-25)