Chemotherapy-induced febrile neutropenia (FN) is a major risk factor for severe infections potentially fatal, and also a dose-limiting toxicity, so causing dose reductions and/or delays in scheduled chemotherapy. This lecture provides recommendations for the use of G-CSF in adult cancer patients at risk of chemotherapy-induced FN. If expected risk of FN is equal or superior to 20%, a primary prophylaxis of FN with G-CSF is recommended. Primary prophylaxis can be considered in case of intermediate 10-20% risk of FN, in presence of factors that increase the frequency/risk of FN, such as age >65, advanced disease, prior episode of FN, poor performance status, radiotherapy to a wide body area (>20%). In case of low risk of FN (<10%), primary prophylaxis is not recommended. We also described the differences in potency and efficacy between two G-CSF, lenograstim (glycosylated) and filgrastim (non-glycosylated), which should be considered when deciding the G-CSF for each patient, particularly in high risk settings for FN.