We have found that the outcome from transplant is improved by using high stem cell doses, and in successive protocols we have achieved progressive improvement in transplant-related mortality from 35% in the first protocol in 1993 to 22% for the latest study. In the last study, in this series, we used the Nexell Isolex 300i system to obtain high CD34+ doses depleted of lymphocytes to a fixed CD3+ T cell dose of 5 x 10(4)/kg. The use of the cell separator and the monoclonal antibodies is covered by IDE 8139. The study focused on the role of cyclosporine in preventing GVHD after T cell depletion. We found that CSA appears to protect against both GVHD and graft failure, with a higher incidence of both complications occurring in patients not receiving CSA.