Unrelated cord blood transplant (CBT) is an alternative treatment option for patients who lack a matched donor. However, the optimal type and intensity of the preparative regimen remains unclear. We evaluated the toxicity and outcomes of a conditioning regimen consisting of melphalan 140 mg/m(2) (day - 8), thiotepa 10 mg/kg (day - 7), fludarabine 160 mg/m(2) over 4 days (days - 6 to - 3) and rabbit antithymocyte globulin (ATG) 1.25 mg/kg (day - 4) and 1.75 mg/kg (day - 3) (FMT). Forty-seven patients with advanced hematologic malignancies with a median age of 23 years (30 adults and 17 children) were treated. Sixty percent of patients were in remission at transplant. Ninety-one percent of the patients engrafted neutrophils after a median of 22 days, and all but one of the patients achieving donor engraftment had hematopoietic recovery with 100% cord blood-derived cells. Grade 3 gastrointestinal toxicity was the major non-hematopoietic toxicity, occurring in 32% of patients. Cumulative incidence of day-100 grade II-IV acute graft-versus-host disease (aGVHD) and chronic graft-versus-host disease (cGVHD) was 53% and 34%, respectively, and non-relapse mortality at day 100 and 2 years was 11% and 40%. Two-year disease-free and overall survival rates were 31% and 44%, respectively. These results suggest that FMT is a feasible conditioning regimen for patients undergoing CBT.