In the present study, to further evaluate the clinical significance of KL-6 in ARDS patients, concentrations of KL-6 in ELF and serum were consecutively measured in 32 patients who developed ARDS in our hospital, and the kinetics of KL-6 levels in ELF and serum during 4 weeks after the diagnosis of ARDS were determined. The gene discussed is MUC1; the disease is acute respiratory distress syndrome.