Speaking from the American Society of Hematology (ASH) 2018 Annual Meeting and Exposition in San Diego, CA, Jonathan Peled, MD, PhD, of Memorial Sloan Kettering Cancer Center, New York, NY, discusses the role of the gut microbiota on the clinical outcomes of hematopoietic cell transplantation (HCT) for the treatment of hematological malignancies. This collaborative study found that patients with low intestinal microbiota diversity have poorer clinical outcomes, and Dr Peled discusses the approaches that could be used to boost diversity.