For several decades, graft-versus-host disease (GVHD) has been a long-standing barrier to successful allogenic hematopoietic cell transplantation and a significant cause of post-transplant morbidity and mortality. Initially described as secondary disease or wasting syndrome in transplanted mice, the pathobiology of GVHD is increasingly understood as a dynamic interplay between innate and adaptive immunity in response to initial tissue damage, leading to inflammation and end-organ damage. In parallel, more uniform symptom capture, diagnosis, and response criteria have facilitated rigorous clinical trial design and conduct; together, these advancements have facilitated the development of novel GVHD prevention and treatment strategies. While these advancements have improved the GVHD treatment paradigm, new questions arise within this complex patient population. This chapter discusses several of the most pertinent current clinical practice challenges in GVHD, including its earlier diagnosis, risk stratification, initial and more advanced stage management, as well as a renewed focus on supportive care, given our increased understanding of key roles played by the human microbiome.