BACKGROUND: The recognition of bronchial asthma as an inflammatory disease led to a search for soluble markers that would be useful in assessing airway inflammation. Interleukin-6 (IL-6) is a representative proinflammatory cytokine that has been shown to be connected with various inflammatory diseases. IL-6 acts via specific receptors that consist of the IL-6 binding glycoprotein gp80 and the signal transducer gp130. In the search for markers of airway inflammation, we investigated the role of soluble interleukin-6 receptor (sIL-6R) and IL-6 in acute asthma. METHODS: Serum levels of sIL-6R and IL-6 were measured in 78 acute asthmatics, in 15 patients with asymptomatic asthma and in 10 healthy control subjects by a specific ELISA using a murine antihuman IL-6R, IL-6 mAb (Quantikine sIL-6R, IL-6). RESULTS: Serum levels of IL-6 in acute asthmatics significantly exeeded those of control subjects. Those of sIL-6R in acute asthmatics were also significantly increased compared to those of control subjects. The serum concentration of IL-6 obtained in acute asthmatics was elevated as compared with the asymptomatic asthmatics. However, Association between eosinophilic count / IgE and IL-6 / sIL-6R in acute asthma could not found. CONCLUSION: Our results suggest that IL-6 may be involved in the pathogenesis of acute asthma and serum levels of IL-6 and sIL-6R may reflect the severity of airway inflammation.