Stem cell transplantation is limited by GVHD and infection and relapse. Increasingly the cell composition of the graft affects outcome new cell separation and culture technology now makes it possible to create clinical grade cell products. This session will focus on the challenges involved in the development of cell therapy products to improve outcome after SCT. It follows the real-life development of three cell therapy product - virus-specific T cells, NK cells and allodepleted T cells, now under evaluation in clinical trials. Essential phases of product development and its many challenges are presented. This session provides a framework for a working model of the process that moves from preclinical studies to completion of a Phase I clinical trial and beyond.