Febrile neutropenia (FN) is a known complication to chemotherapy during breast cancer treatment. The immune system is alongside the tumour mass vulnerable for the cytotoxic effect of antineoplastic agents. This induced state of neutropenia leads to increased bacterial and fungal susceptibility. Febrile neutropenia is defined by a low neutrophil count (<0.5 x 109/L) and a fever of ¡Ý38.5 ¡ã C. In over 50 % of these cases, there is a manifest or occult infection in the organism. Due to the decimation of the immune system, there is often little clinical symptoms related to the infectious state. The prescence of fever is for this reason a cornerstone in the diagnosis of infection in the neutropenic patient. We did a retrospective clinical study of 120 patients that underwent FEC chemotherapy in a adjuvant/palliative/neoadjuvant situation for breast cancer at the Oncologic department at Ullevaal University Hospital. We found a prevalence of NCI-grade 4 neutropenia in 4.9 % and NCI-grade 4 leucopenia in 1.5 % of measured blood values at nadir. This led to a total of 6 patients (5 %) experiencing an episode of febrile neutropenia. 2 of these patients belonged to the adjuvant group of 99 patients, giving a prevalence of FN in this subgroup of 2%. On this background, one could argue that a frequent evaluation of leukocyte/granulocyte nadir blood values is unnecessary in this subgroup. Furthermore, this does not apply to the first nadir count, as it has value in predicting risk of developing subsequent neutropenic complications.