The introduction of a WHO Standard for serumferritin effected a standardisation of different methods, improving quality and security for clinical routine diagnostic purposes. Therefore the clinical evaluation of serumferritin gained even more importance. For Evaluation of iron stores of children, pregnant women, population studies, patients on hemodialysis or patients with rheumatoid arthritis low serumferritin values give safe results. In addition serumferritin is of clinical usefulness in monitoring therapy of both iron deficiency and iron overload. Evaluating a single serumferritin value one should consider the total clinical situation of the patient. As some tumors can produce and secrete serumferritin, e. g. acute myeloblastic leukemia, germ cell tumors, malignant melanoma, serumferritin might be helpful in monitoring the malignant disease. The ongoing characterization of tissue isoferritin, especially acidic isoferritin, may eventually lead to a clinically significant diagnostic marker of neoplasia.