Authors evaluated of the species of bacteria isolated in the blood cultures of patients with febrile neutropenia suffered from acut myeloid and acut lymphoid leukaemia in the Haematology Department of the University of Szeged between 2002 and 2003. One hundred and one febrile episodes of 54 patients were treated and examined for their blood cultures during the examined period. Out of 75 cases Gram-positive cocci was 53%, Gram-negative rods were 35% (21% enteric rods, 4% Gram-positive aerob nonsporiform rods – Corynebacterium jeikeum – 5% anaerobs and 5% others) and 3% were candida. No duplicate involved into the data. It is important to know the spectrum of the bacteria to select the effective empiric therapy.