Determination of mTREM-1 expression on monocytes has been investigated as a perspective diagnostic method to distinguish infectious from non-infectious etiology of the inflammation. The aims of our study were: i) to investigate the expression of TREM-1 on monocytes in septic patients and in those after elective spinal surgery without infection; ii) to assess the dynamics of mTREM-1 expression on monocytes and its association with the outcome in patients with severe sepsis.