Allogeneic haematopoietic cell transplantation holds the potential for treatment of many malignant and nonmalignant haematologic diseases. Graft-versus-host disease (GvHD), however, is a common complication after transplantation and remains a major cause of morbidity and mortality. In steroid-refractory acute GvHD, mortality rates approach 85%. In some countries, MSC (mesenchymal stromal/stem cells) therapy products are already available as medicinal products with marketing authorisation approval because of their potent immunomodulatory and regenerative capacity.