The main risk factors of infectious complications in cancer patients result from immune deficiency more or less related to cancer. Prognosis is related to the type and grade of the underlying disease. Prospective studies should be conducted to update data on the frequency of infections, morbidity and mortality (expert agreement). Prospective studies are needed to follow the epidemiology in cancer patients, particularly in neutropenic patients (expert agreement). Prospective studies should be conducted to determine prognosis factors allowing precise recognition of "low-risk" neutropenic patients with fever who could benefit from home care (expert agreement). When infection is suspected, the first criterion determining the therapeutic attitude concern signs of gravity requiring emergency care (septic shock). Beyond this situation, the first criterion determining the therapeutic attitude is the severity of the neutropenia. Microbial diagnosis is essential for initiating and later adapting anti-infectious treatment as well as for assessing efficacy.