The term leucopenia describes a decrease in the number of leucocytes in the blood circulation, defined as less than 4x109 per L (normál leucocytes level). Three deficiency states exist as defined by the type of leucocyte that is affected: neutropenia, granulocytopenia (or agranulocytosis) and lymphocytopenia. Neutropenia can be acquired or, less commonly, congenital. Acquired neutropenia is very often caused by infecti-on or medication (drug-induced neutropenia). The most common cause of severe neutropenia is bacterial sepsis, viruses (infectious mononucleosis and hepatitis B virus). Drug-induced neutropenia usually results from exposure to chemotherapeutics, thyroid inhibitors, antibiotics, analgesics/antiinflammatory agents, or neuropsychotropics. In addition we can find neutropenia in patients with systemic diseases (lupus erythe-matosus), hypersplenism, antileucocyte antibodies or bone marrow infiltration. In the differential diagnostic process it is always necessary to assess the level and the extent of neutropenia, alternatively further numerical and morphological changes in blood count, dynamics of the disease, symptoms of infection ete. The cause of neutropenia should be determined as soon as possible to start the appropriate treatment. This survey shows a list of possible causes, evaluation and management of neutropenia

        Key words: blood count, leucopenia, neutropenia, agranulocytosis.