A disintegrin and metalloproteinase 19 (ADAM19, or adamalysin 19) is a cell surface glycoprotein with a signal sequence, a prodomain, a metalloproteinase domain, a disintegrin domain, a cysteine-rich domain, a epidermal growth factor-like domain, a transmembrane domain, and a cytoplasmic domain. It is an endopeptidase that cleaves extracellular matrix proteins and sheds growth factors and cytokines such as neuregulins, heparin-binding epidermal growth factor, tumor necrosis factor (TNF)-α, and TNF-related activation-induced cytokine. The ADAM19 gene was cloned from human, monkey, and mouse. It is expressed in multiple organs and tissues including heart, lung, bones, brain, spleen, liver, skeletal muscle, kidney, and testes. ADAM19 plays essential roles in embryo implantation, cardiovascular morphogenesis, neurogenesis, and other developmental processes. It has constitutive α-secretase activity associated with processing Alzheimers disease amyloid precursor protein (APP) to non-amyloidogenic fragments; thus, it is neuroprotective. Those observations indicate that inhibition of ADAM19 activity is undesirable during embryo development and morphogenesis, and during the development of Alzheimers disease. On the contrary, in adults, ADAM19 is upregulated in human brain tumors such as astrocytoma and glioblastoma and is correlated with the invasiveness of glioma. It is also over-expressed by many human cancerous cell lines including cancers of the colon, ovary, lung, and brain. Abnormally high expression of ADAM19 is also linked to inflammation and fibrosis of the lung and kidney. Targeted inhibition of ADAM19 may be crucial for the treatment of certain types of tumors and inflammatory diseases.