Proteinase-activated receptors (PARs) are novel G-protein-coupled receptors activated by serine and other proteinases to induce changes in cellular function. There is extensive evidence that PARs are expressed in the airways in a variety of cell types that are relevant to inflammatory lung diseases, and that activation of these receptors might be linked to significant pathological changes. Thus, PARs are exciting new targets in lung disease research. However, much of the data to date has come from in vitro studies using limited pharmacological tools, and considerably more needs to be known about the functions of this family of receptors in the lung before their potential as drug targets can be established.