Graft versus host disease (GvHD) is a generalised immune system reaction following allogeneic hematopoietic stem cell transplantation (AHSCT) in patients with acquired and congenital hematopoietic system disorders. Vijayanand Rajendran et al. of Europital look at how the current focus is on developing and validating new biomarkers, and pursuing clinical trials of new agents which are effective, but less toxic, to develop more targeted treatments for GvHD and achieve better and safer alloHSCT treatment.