This trial is designed to evaluate the use of stem cells from a matched sibling in reducing the incidence of graft versus host disease (GVHD) in the treatment of haematological malignancy.The trial is being conducted by the Royal Brisbane and Women's Hospital in conjunction with the Queensland Institute of Medical Research. The trial started in June 2004 and proposes to enrol 47 patients with a haematological malignancy that requires chemotherapy and bone marrow transplant. Participants require a sibling with an identical HLA match as a donor for this trial. Donors will receive an injection of pegylated GCSF to release bone marrow stem cells into the circulation. The stem cells will be isolated from the donor's blood and provided to the trial participant once they have received their chemotherapy The patient will then be monitored for complications including for acute GVHD.