Background.The development of strategies to enhance survival of transplanted organs and to potentially lower or even discontinue immunosuppressive therapy would represent a significant advance in posttransplant patient care. The aim of this clinical trial was to determine the effect of timing and dose of peripheral donor bone marrow cell (DBMC) infusion on graft and patient survival after liver transplantation.Methods.DBMC, obtained from vertebral bodies, were administered in 101 recipients of liver allografts (OLTX). There were 107 patients for whom DBMC could not be obtained; they received OLTX alone (controls). A total of 5×108/kg DBMC were infused at day 0 (group 1; n=9); at days 0 and 11 (group 2; n=26); or at days 5 and 11 (group 3; n=26). In group 4 (n=40), patients received up to five infusions of 2×108/kg DBMC at days 5, 14, 21, 28, and 90 after OLTX.Results.When the results from patients receiving two or more DBMC infusions (groups 2, 3, and 4) are considered, both patient and graft survival were significantly improved compared with the control group (P=0.02 andP=0.01, respectively). In groups 3 and 4, 88.5% and 95% of patients were alive with mean follow-up of 536 and 265 days, respectively, compared with 77.6% of patients in the control group (average follow-up of 452 days) (P=0.02). Graft survival was also significantly improved in groups 3 (88.5%) and 4 (92.5%), compared with the controls (72%) (P=0.007).Conclusions.The results suggest that dose and timing of DBMC infusions may be important variables affecting allograft survival. A randomized prospective trial is now in progress to compare group 3 DBMC infusion protocol with controls receiving OLTX alone.