Pseudomelanosis duodeni is a rare benign condition in which dark pigments accumulate in macrophages located in the lamina propria of the duodenal mucosa. Most reported cases had hypertension with or without chronic renal failure, and were taking antihypertensive agents and iron supplements. Therefore, it has been assumed that pseudomelanosis duodeni is associated with these medications. Our case was a 77 year-old female patient diagnosed as having hypertension, congestive heart failure, iron deficiency anemia, and depression, who had been treated with antihypertensive agents and iron supplement. Upper gastrointestinal endoscopy revealed many tiny discrete dark macules scattered throughout the first and second portions of the duodenum. Endoscopic mucosal biopsy disclosed macrophages with Prussian blue and Fontana- Masson stain positive pigments, which suggested that the nature of pigment was iron sulfide. (Korean J Gastrointest Endosc 2004;28:3942)