 2.4. Data generated in our hospital enhance the evidence of feasibility of hematopoietic engraftment across the HLA-haplotype barrier in adult patients after RIC.28 Between April 2004 and February 2008, 31 patients including 21 patients with acute leukemia underwent HLA-haploidentical HCT after RIC of busulfan, fludarabine, and ATG and all 28 evaluable patients achieved engraftment with absolute lymphocyte count ANC over 500μl on median day 16.5. As early as 2 weeks after HCT, 22 of 24 evaluated patients showed complete donor chimerism of 95 or over. None of the patients in the study experienced secondary graft failure. While achieving consistent and durable donor cell engraftment, the cumulative incidences of grades 2-4 acute and chronic GVHD were 19, and 20, respectively. 