The causes of iron deficiency anemia in a population of adults admitted to two Jerusalem hospitals within a period of 7 years were examined. About one half of the 262 patients with iron deficiency anemia were over 70 years old. The ratio of males to females exclusive of young females with menorrhagia was 1:1.8. Despite the combined use of various diagnostic procedures, no definite cause of iron deficiency anemia could be established in 34% of patients. Benign gastrointestinal lesions were found in about one half of the cases in both hospitals. The prevalence of GI neoplasms in hospital B with a more intensive use of endoscopic procedures was significantly higher than in hospital A (18% vs 5%, p less than 0.001). The relative usefulness of barium contrast vs endoscopic studies is illustrated by the fact that 22 diagnoses established by endoscopy were missed by barium studies, whereas only 2 of those established by barium studies were not visualized by endoscopy. A particularly high risk group were anemic males aged 50 to 69 years in whom the prevalence of GI neoplasms was 30%. These data indicate that reliance on traditional contrast radioscopy may result in misdiagnosis of a high proportion of gastrointestinal neoplasms.