Alterations of gut bacterial microbiota composition (mycobiota) have been associated with outcome after allogeneic hematopoietic stem cell transplantation (allo-HSCT), however the impact of the gut mycobiota is still unknown in the allo-HSCT setting. Mohamad Mohty, MD, PhD, Saint-Antoine Hospital, Paris, France, discusses a study that examined the role of fecal mycobiota in patients undergoing allo-HSCT. Prof. Mohty highlights the low fungal diversity in allo-HSCT patients and the future perspectives for this novel field of investigation. This interview took place at the American Society of Hematology (ASH) 2019 Annual Meeting and Exposition in Orlando, FL.