Assay of cytokines and C reactive protein (CRP) in different periods of febrile neutropenia may be helpful for early defining the risk in severe infections. We determined serum interleukin-6 (IL-6), interleukin-8 (IL-8), soluble interleukin-2 receptor (sIL-2R), tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and CRP in 22 previously untreated patients with various malignancies. Samples were obtained in four different clinical periods of febrile neutropenia; prior to chemotherapy, afebrile neutropenic period after chemotherapy, febrile neutropenic period, and recovery period. When compared to sex-and age-matched group of healthy subjects, IL-6, IL-8, sIL-2R, and CRP levels were found to be elevated in all periods. The highest levels were encountered in the febrile neutropenic period. For predictivity purposes, the afebrile neutropenic period was the most important period. Serum sIL-2R, IL-6, IL-8 and CRP levels were elevated in this period. IL-8 levels showed the most stable elevation through different stages of febrile neutropenia. Serum IL-8 levels were found to have the most reliable and stable elevation in different clinical stages of febrile neutropenia. Nevertheless, IL-8 is not able to discriminate among risk groups and cannot be used as a predictive factor.