Recent advances in the instrumentation and techniques of enteroscopy now permit examination of the small bowel. This report is on the use of a prototypic small bowel enteroscopy to investigate patients with gastrointestinal bleeding of obscure origin. We used the sonde-type enteroscope (Olympus Corp.) that migrates distally responding to peristaltic activity. This instrument has neither tip deflection controls nor interventional capability. Small bowel enteroscopy was performed in 17 patients. Arteriovenous malformations were visualized in 5 patients but three of them suffered from Rendu-Osler disease. Small bowel enteroscopy can be useful in the evaluation of patients with gastrointestinal bleeding of obscure origin. However, patients must be well selected on basis of negative routine examinations because this method is time-consuming.