Florent Malard, MD, PhD, Saint Antoine Hospital, Paris, France, gives an overview of his talk on the role of the microbiota in the context of hematopoietic stem cell transplantation (HSCT), as presented at EBMT 2021. Many studies have highlighted an association between the microbiota and patient outcomes for patients undergoing HSCT. Dr Malard outlines evidence that the microbiota impacts the regulation of hematopoiesis, and that antibiotics can impair hematopoietic reconstitution, resulting in a reduced number of hematopoietic stem cells. Dr Malard also discusses strategies for reducing these impacts, such as reducing the use of antibiotics, and fecal microbiota transplantations. This interview took place during the 47th Annual Meeting of the European Group for Blood and Marrow Transplantation (EBMT) 2021.