Cytokines, especially tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6) play an important role in the genesis and progression of the septic shock syndrome. We performed a study monitoring levels of these three cytokines in ten neutropenic oncology patients in whom an infectious syndrome was suspected. A comparison was made with a population of nine non-neutropenic patients on the intensive care unit. Unfortunately the results of this study do not allow specific profiles to be established for each cytokine in the populations studied. Levels of IL-6, TNF alpha and IL-1 beta were not statistically higher in the non-neutropenic patients when compared with the neutropenic group. However, the highest IL-6 levels were observed for four non-neutropenic patients, three of whom died. High levels of C-reactive protein (CRP), haptoglobin and fibrinogen were found, reflecting the inflammatory status of each patient. CRP levels were higher in the non-neutropenic patients and correlated with IL-6 levels, indicating the importance of CRP determination in this group of patients.