The physiology of iron homeostasis, clinical presentation, diagnosis, differential diagnosis and therapeutic options in iron-deficiency anemia are discussed. Iron deficiency is the most common haematological disorder encountered in general practice and iron-deficiency anemia is the most frequently occurring anemia throughout the world. Blood loss is a major cause of iron-deficiency anemia. Gastrointestinal bleeding is the most common cause of iron deficiency in adult men and is second only to menstrual blood loss as a cause in women. Iron-deficiency anemia is not a disease itself but a manifestation of an underlying disease, searching for the latter is therefore crucial and may be of far greater importance to the ultimate well-being of the patient than repleting iron stores. The symptoms and signs of iron deficiency are partially explained by the presence of anemia. However, there also appears to be a direct effect of iron deficiency on the central nervous system. The most important screening investigations for iron deficiency in clinical practice are the haemoglobin, the haematocrit and the mean corpuscular volume (MCV). The single most important measure of iron status is the serum ferritin, values below the lower limit of normal being specific for iron deficiency. In inflammation, hepatopathy and haemolysis serum ferritin is also released leading to falsely elevated values, therefore an analysis of the C-reactive protein (CRP) should always accompany the analysis of serum ferritin. Repleting iron stores is usually done with oral iron therapy, the available preparations are comparable with respect to efficacy, side effects and costs. The main indications for parenteral iron therapy are intolerance to oral iron, intestinal malabsorption and poor compliance to an oral regimen. The iron sucrose preparation should bepreferentially used for that purpose, the total dose is calculated from the amount of iron needed to restore the haemoglobin deficit plus an additional amount to replenish iron stores.