Peripheral blood stem cell transplantation is a treatment which involve first harvesting specific cells called stem cells from the peripheral blood of the donor. These cells are harvested by a type of filtration and then preserved, usually by freezing, and finally given to the recipient after he or she has received intensive treatment. The stem cells are usually given instead of bone marrow cells. They go to the recipient's bone marrow spaces and rebuild the bone marrow after the intensive treatment is over. The treatment does not involve surgery, but is nevertheless a form of transplantation.