Stem cells normally populate the bone marrow. Drugs are used to encourage stem cells to go into the peripheral blood, a process call mobilization. In the peripheral blood stem cells can be collected and subsequently transplanted. In Canada, the only drug used to mobilize stem cells from donors is filgrastim, a form of granulocyte colony stimulating factor (G-CSF). Although well tolerated, there are some shortcomings to this agent and there is clearly room to improve in terms of the donor experience and providing the optimal stem cell graft.