OBJECTIVES: Granulocyte-macrophage colony stimulating factor (GM-CSF) is a keyregulator cytokine that modulates the proliferation and maturation ofpolymorphonuclear and mononuclear progenitors. This study was designed toinvestigate and clarify the role of GM-CSF in 52 critically ill patients withsystemic inflammatory response syndrome (SIRS).METHODS: Serum levels of GM-CSF were detected by an immunoenzyme assay.RESULTS: Our results clearly show that the serum concentrations of GM-CSF weresignificantly elevated in patients with infectious and noninfectious SIRS(33.2+/-45.7pg/ml, controls: 17.2+/-9.8pg/ml; p=0.0303). In addition, GM-CSFlevels significantly decreased in patients with SIRS, particularly in patientswith infectious SIRS, 5 and 7 days later. There was a clear tendency towardhigher levels of GM-CSF in patients with poor, as compared with those having agood outcome of the disease.CONCLUSION: These results show that GM-CSF may play an important role in patientswith infectious and noninfectious SIRS, and that GM-CSF levels progressively and significantly decrease in patients with infectious SIRS.