Although haematopoietic stem cell transplantation (HSCT) is a powerful treatment modality, it is a blunt instrument against cancer and diseases of the haematopoietic and immune system. Various techniques have been developed to engineer the haematopoietic stem cell (HSC) graft to enable it to perform its task more effectively. These techniques include the removal of cells which cause graft-versus-host disease (GVHD), the eradication of cells which might cause relapse, the expansion of donor cells when there is an inadequate cell dose, and the addition of selected cells to improve graft function. In this review, we will discuss each of these means of haematopoietic graft manipulation in turn and then touch on some regulatory requirements in the field of haematopoietic graft engineering. While the science is still prepubescent, it has passed its infancy and further developments in the next decade or so should allow it to be taken to a wider scale to benefit more patients.