GATA3 is a transcription factor that in humans is encoded by the GATA3 gene. Studies in animal models and humans indicate that it controls the expression of a wide range of biologically and clinically important genes. The GATA3 transcription factor is critical for the embryonic development of various tissues as well as for inflammatory and humoral immune responses and the proper functioning of the endothelium of blood vessels. GATA3 haploinsufficiency (i.e. lose of one or the two inherited GATA3 genes) results in a congenital disorder termed the Barakat syndrome. Current clinical and laboratory research is focusing on determining the benefits of directly or indirectly blocking the action of GATA3 in inflammatory and allergic diseases such as asthma. It is also proposed to be a clinically important marker for various types of cancer, particularly those of the breast. However, the role, if any, of GATA3 in the development of these cancers is under study and remains unclear.