Relapse due to either residual host disease or reinfused tumor cells remains the principal cause of treatment failure after autologous stem cell transplantation. Although it is intuitively attractive to remove putative tumor cells from autologous grafts prior to transplant and more than 1000 articles have been written on the subject, there are only limited data suggesting that purging autografts has any favorable effect on relapses or disease-free survival. Certain purging techniques that remove substantial numbers of T cells or destroy progenitor cells may have adverse effects such as delayed hematopoietic or T cell reconstitution. There is a critical need for large, well-designed trials that specifically address the value of a particular purging technique on relapses and disease-free survival after autologous stem cell transplant.