A 31-year-old man with recurrent attacks of hypoglycemia was hospitalized with the clinical suspicion of an insulinoma. Computed tomography and conventional (transabdominal) ultrasound were doubtful, showing a small solid low-density mass probably originating from the tail of the pancreas. Selective angiography and transhepatic venous sampling for pancreatic hormone assay were not discriminant. Finally, an endoscopic ultrasonographic examination, allowing a better visualization of the pancreas, established with certainty the origin of the lesion from the tail of the gland. This was subsequently confirmed at operation.