Many hematologists still rely on the assessment of stainable iron on aspirated marrow smears or biopsy for the definitive diagnosis of iron deficiency anemia. Although still widely regarded as the gold standard for the diagnosis of iron deficiency, the reliability of the marrow iron stain is. Often suboptimal when used for routine clinical purposes. In a recent study, 108 consecutive bone marrow specimens from unselected hematology patients reported to have absent iron were reviewed.ⁱ⁰ One-third of the reports were incorrect due either to an inadequate specimen or detectable iron stores, and less than half of the patients with absent marrow iron had clinical evidence that supported the diagnosis of iron deficiency anemia. In another recent review of iron stains, high intra-observer variability in pathological diagnosis led the authors to conclude that the bone marrow is not a perfect gold standard.⁴ It should also be noted that the bone marrow is no longer reliable in diagnosing iron deficiency anemia after parenteral iron therapy. While marrow iron staining continues to play a critical role in validating newer laboratory measurements of iron status when performed and reviewed under standardized conditions in prospective studies by experienced investigators, bone marrow examinations should seldom be performed solely to diagnose iron deficiency because of the expense, discomfort, and technical pitfalls with this approach.