Members of the human serpin family regulate a diverse array of serine and cysteine proteinases associated with essential biological processes such as fibrinolysis, coagulation, inflammation, cell mobility, cellular differentiation, and apoptosis. Most serpins are secreted and attain physiologic concentrations in the blood and extracellular fluids. However, a subset of the serpin superfamily, the ov-serpins, also resides intracellularly. Differential display was used to identify a novel serpin (headpin or SERPINB13) that is underexpressed in squamous cell cancers of the oral cavity. SERPINB13 is expressed in normal oral mucosal tissue, skin, and cultured keratinocytes.