The serine proteinase inhibitors (serpins) compose a superfamily of proteins with a diverse set of functions, including the control of blood coagulation, complement activation, programmed cell death and development. Serpins are secreted glycoproteins that contain a stretch of peptide that mimics a true substrate for a corresponding serine protease. SerpinB11 (serpin peptidase inhibitor, clade B (ovalbumin), member 11), also known as EPIPIN or SERPIN11, is a 392 amino acid cytoplasmic protein that belongs to the Ov-serpin subfamily and serpin family. Like other members of the serpin family, SerpinB11 has been identified as a noninhibitory intracellular protein. The gene encoding SerpinB11 maps to human chromosome 18, which houses over 300 protein-coding genes and contains nearly 76 million bases. There are a variety of diseases associated with defects in chromosome 18-localized genes, some of which include Trisomy 18 (also known as Edwards syndrome), Niemann-Pick disease, hereditary hemorrhagic telangiectasia, erythropoietic protoporphyria and follicular lymphomas.