Gastrointestinal bleeding is believed to cause iron-deficiency anemia (IDA). The information concerning ideal evaluation of the gastrointestinal tract and exact findings in patients with IDA is scant. The aim of this study was to prospectively evaluate patients with IDA for gastrointestinal lesions potentially causing IDA at a US Army Teaching Medical Center with Gastroenterology Fellowship. Seventy patients with IDA had esophagogastroduodenoscopy (EGD) and colonoscopy, and if this evaluation was unremarkable, then small bowel biopsy was obtained at EGD to evaluate for celiac disease. Enteroclysis was done if endoscopic evaluation was negative. At endoscopy, at least one lesion potentially accounted for the IDA in 50 (71%) patients. At colonoscopy, 21 (30%) patients had 22 lesions (four colon cancer, seven adenoma > 1 cm, six vascular malformation, four severely bleeding hemorrhoids, one ileal Crohn's); at EGD, 39 (56%) patients had 43 lesions (11 gastric erosion, 10 esophagitis, four vascular malformation, four celiac disease, three gastric cancer, three gastric ulcer, three duodenal ulcer, two gastric polyp > 1 cm, one duodenal lymphoma, one esophageal cancer, and one duodenal Crohn's). Twelve (17%) patients had both upper and lower gastrointestinal tract lesions. Twenty-four of 32 (75%) patients with positive fecal occult blood test had potentially bleeding lesions compared to 24 of 38 (63%) patients with negative fecal occult blood test (P > 0.05). Six of nine patients with malignancy had positive fecal occult blood test. Twenty patients with normal endoscopy and small bowel biopsy had normal enteroclysis.(ABSTRACT TRUNCATED AT 250 WORDS)