Alendronate sodium (FosamaxⰒ) is an aminophosphonate used in treatment of postmenopausal osteoporosis by inhibition of osteoclastic activity. Esophageal ulcers related to alendronate use have been reported at the rate of 2∼6%. However, there have been no reports of esophagitis or esophageal ulcer by alendronate in Korea. We present a case of esophageal ulcer caused by alendronate. The patient presented with retrosternal pain and severe odynophagia for a few days. Esophagogastroduodenoscopy revealed multiple deep ulcers at the esophagus. Her symptoms resolved completely after stopping alendronate. A follow-up esophagogastroduodenoscopy 6 weeks later revealed complete healing of the ulcers. (Korean J Gastrointest Endosc 2004;28:2528)