Kallikrein-8, also known as Neuropsin, Serine protease 19, Serine protease TADG-14, Tumor-associated differentially expressed gene 14 protein, and KLK8 is a secreted protein that belongs to the peptidase S1 family and Kallikrein subfamily. It is a serine protease that is capable of degrading some proteins such as casein, fibrinogen, kininogen, fibronectin, and collagen type IV. Kallikrein-8 / KLK8 plays a role in the formation and maturation of orphan and small synaptic boutons in the Schaffer-collateral pathway. It regulates Schaffer-collateral long-term potentiation in the hippocampus and is required for memory acquisition and synaptic plasticity. It is involved in skin desquamation and keratinocyte proliferation and plays a role in the secondary phase of pathogenesis following spinal cord injury. It also cleaves L1CAM in response to increased neural activity. It induces neurite outgrowth and fasciculation of cultured hippocampal neurons. Kallikrein-8 / KLK8 is expressed at high levels in serum, ascites fluid, and tumor cytosol of advanced-stage ovarian cancer patients and may serve as a marker of ovarian cancer. Kallikrein-8 / KLK8 may have potential clinical value for disease diagnosis or prognosis and it may also be a useful therapeutic target.