Sepsis is a common cause of morbidity and mortality in intensive care units. Unfortunately, there is no gold standard for diagnosing sepsis as clinical and laboratory signs are neither sensitive enough nor specific enough, and microbiological studies often remain negative. Thus, there is a need for clinical or laboratory tools to distinguish between sepsis and non-infectious inflammatory disorders. Among the potentially useful markers of sepsis, procalcitonin has been suggested to be the most promising, although results are variable depending on the severity of illness and degree of infection in the patient population studied. The triggering receptor expressed on myeloid cells-1 (TREM-1) is a member of the immunoglobulin superfamily, of which expression is upregulated on phagocytic cells in the presence of bacteria or fungi. Here we report on the potential usefulness of assessing the soluble form of TREM-1 (sTREM-1) in biological fluids for the diagnosis of microbial infection.