The multicenter study conducted by Lorente and coworkers published in the previous issue of Critical Care demonstrates that matrix metalloproteinase (MMP)-9 and MMP-10 and their inhibitor tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) are promising novel biomarkers to predict severity and outcome of sepsis. In recent years MMPs have emerged as biomarkers in a variety of diseases, such as sepsis, coronary artery disease, cancer, heart failure, chronic lung disease and rheumatoid arthritis. MMPs constitute a family of proteinases that are expressed during developmental, physiological, and pathophysiological processes, for example as a response to infection. Excessive inflammation following infection may cause tissue damage, and MMPs are implicated in causing this immunopathology. The activity of MMPs is regulated by secretion of specific inhibitors (TIMPs). Studies using MMP inhibitors and MMP knockout mice indicate that MMPs play an essential role in infection and in the host response to infection. The measurement of MMP-9 and MMP-10 and their inhibitor TIMP-1 in the intensive care setting could be an attractive noninvasive tool for determination of outcome of septic patients.