The study will be conducted in the University Hospital of the Federal University of Minas Gerais, Brazil. This is a 600-bed tertiary hospital, with approximately 1.6 thousands hospitalizations/month. Roughly 120 episodes of febrile neutropenia were recorded in the first semester of 2007, occurring in 100 patients with hematological leucosis or post-BMT. This number rises if one considers other groups of neutropenic patients, such as those with neutropenia due chemotherapy for solid tumors, patients with BM aplasia, myelo dysplasia, among others,