XDx Inc. is a molecular diagnostics company based in South San Francisco, California. Setting the stage for a new era in personalized medicine, XDx is one of the first companies to develop and commercialise practical applications built on insights from the Human Genome Project. The company has developed a proprietary new method to non-invasively monitor the immune system by measuring gene expression in a patient's peripheral blood. The first application, AlloMap™ Molecular Expression testing specifically addresses the needs of clinicians and patients in the post-cardiac transplantation patient management market. This test is commercially available.