Kallikrein 11 is expressed in brain, skin, ovary and prostate. Increased levels of Kallikrein 11 have been reported in prostate and ovarian carcinoma. It is a serine protease. Kallikrein 11 (KLK11), also known as hippostasin, trypsin-like serine protease and PRSS20, is a member of human tissue kallikrein family.6 Two alternatively spliced forms exist, resulting in 250 (isoform 1) and 282 (isoform 2) amino acid sequences, respectively.1-4. Isoform 1 consists of a signal peptide (residues 1-18), a short pro peptide (residues 19-21) and the mature chain (residues 22-250). Isoform 2 is identical to isoform 1, except that a 32 amino acid segment is inserted in isoform 2 before residue1 in isoform 1. Isoform 1 is predominantly expressed in brain whereas isoform 2 is preferentially expressed in prostate. KLK11 is a novel marker for ovarian and prostate cancer carcinomas.7-9 rhKLK11, after being activated by thermolysin, is active against a thioester substrate.