Iron-deficiency anemia is a common reason for referral to a gastroenterologist. In adult men and postmenopausal women, gastrointestinal tract pathology is often the cause of iron-deficiency anemia, so patients are frequently referred for endoscopic evaluation. Endoscopy may be costly and at times difficult for the patient. Therefore, physicians need to know what lesions can be identified reliably and, more importantly, the importance of ruling out life-threatening conditions such as occult malignancy. Over the past decade, a number of prospective studies have been completed that examined the yield of endoscopy in the investigation of iron-deficiency anemia. The present article provides a broad overview of iron-deficiency anemia, with particular emphasis on hematological diagnosis, etiology, the use of endoscopy in identifying lesions and iron-repletion therapy. Other clinical scenarios, including assessment of patients on anti-inflammatory or anticoagulation therapy and patients with bleeding of obscure origin, are also addressed. The present article provides a diagnostic algorithm to iron-deficiency anemia, which describes a more systematic manner in which to approach iron-deficiency anemia.