Abstract:Sixteen patients with hematological malignancy received cyclophosphamide (120 mg/kg), fractionated total body irradiation (12 Gy), oral cyclosporin, and an HLA‐identical sibling marrow transplant depleted of T cells by incubation with the monoclonal antibody anti‐HuLy‐m1 (CD2) and rabbit complement with (five patients) or without (11 patients) anti‐HuLy‐m8 (CD8). These 16 patients were compared historically to 84 patients with hematological malignancy receiving cyclophosphamide (120 mg/kg), fractionated total body irradiation (12 or 14 Gy), oral cyclosporin, and unmanipulated HLA‐identical sibling marrow, for parameters of engraftment and graft‐versus‐host disease (GVHD). Graft failure occurred in one of the 16 T‐cell depleted recipients and in one of the 84 non‐depleted recipients. Engraftment was slightly but significantly slower in the T‐cell depleted group and bacterial infections significantly more, frequent and severe than in the unmanipulated group. There was a suggestion that the severity of acute GVHD was reduced in those receiving T depleted marrow. Randomized trials will be necessary to determine if marrow T‐cell depletion results in superior long‐te