We carried out a randomized, multicenter study comparing the inception of cyclosporine- A (CsA) on day -7 to conventional CsA (on day -1) to evaluate the influence of this modification on graft-versus-host disease (GVHD), treatment-related mortality (TRM), relapse rate (RR), and event-free survival (EFS) in children with hematologic malignancies given unrelated donor (UD) hematopoietic stem cell transplantation (HSCT). Between 1997 and 2002, 152 children transplanted for acute leukemia (102), myelodysplastic syndromes (23), chronic myelogenous leukemia (20), and non-Hodgkin lymphoma (7) were enrolled in the study and randomized to receive either early CsA (group 1, N = 72) or conventional CsA (group 2, N = 80), after stratification according to HLA compatibility and disease phase. The cumulative incidence of both grade II-IV and grade II-IV acute GVHD (aGVHD), as well as of chronic GVHD (cGVHD), did not differ between the 2 groups. No significant differences were observed also with regard to TRM and RR. The 8-year Kaplan-Meier estimates of EFS were 56% in group 1, and 46% in group 2 (P = NS). In the Cox model, advanced disease phase, male recipient, older donor, and occurrence of grade III-IV aGVHD predicted inferior overall EFS. These data indicate that early inception of CsA does not improve posttransplantation outcome of children with hematologic malignancies given UD-HSCT.