Patient Inclusion Criteria:

One of the following diagnoses:

* Acute myelogenous leukemia at the following stages: first remission, second remission, third or subsequent remission, or not in remission
* Acute lymphoblastic leukemia at the following stages: first remission, second remission, third or subsequent remission, or not in remission
* Chronic myelogenous leukemia at the following stages: chronic phase, accelerated phase, or blast phase
* Myelodysplastic syndromes (MDS) at the following stages: refractory anemia; refractory anemia with ringed sideroblasts; refractory cytopenia with multilineage dysplasia; refractory cytopenia with multilineage dysplasia and ringed sideroblasts; refractory anemia with excess blasts-1 (5-10% blasts); refractory anemia with excess blasts-2 (10-20% blasts); myelodysplastic syndrome, unclassified; or MDS associated with isolated del (5q)
* Myeloproliferative diseases: chronic myelomonocytic leukemia; agnogenic myeloid metaplasia with myelofibrosis (idiopathic myelofibrosis); juvenile myelomonocytic leukemia
* Therapy-related acute myelogenous leukemia (AML) or MDS with prior malignancy that has been in remission for at least 12 months. If the remission is less than 12 months, Medical Monitor or Protocol Chair approval is required for eligibility

Patient Exclusion Criteria:

* Prior allogeneic or autologous transplants using any hematopoietic stem cell source; patients with secondary malignancies who have had a prior autologous transplant will be eligible; the prior autologous transplant must have been performed for the primary malignancy (such as lymphoma) and must have occurred 12 or more months prior to enrollment
* Lymphoma (11% of 2001 NMDP transplants), other malignant disorders (6%), and non-malignant disorders (9%)

Donor Inclusion Criteria:

* Matched for HLA-A, B, and DRB1 antigens

1. One antigen mismatch at HLA-A, B, or DRB1 is acceptable with or without mismatch at HLA-C
2. Typing is by DNA techniques: intermediate resolution for A, B, and C, and high resolution for DRB1. HLA-C typing is mandatory but will not count in the match.
* Willing to undergo both bone marrow harvest and G-CSF administration with apheresis
* Willing to be randomly assigned to either marrow or PBSC collection
* Adequate peripheral venous access for leukapheresis or willing to undergo placement of a central catheter
* Donor center affiliation with NMDP
* Additional donor inclusion criteria can be found in the Donor Companion Manual

Donor Exclusion Criteria:

* Pregnant (positive serum β-HCG) or uninterruptible breastfeeding
* Known allergy to G-CSF or to E. Coli-derived recombinant protein products
* History of autoimmune disorders
* History of deep vein thrombosis or venous thromboembolism
* History of iritis or episcleritis
* History of serious adverse reaction to anesthesia
* Thrombocytopenia (platelets less than 150,000 per mcL) at baseline evaluation
* Current treatment with lithium
* Presence of sickle hemoglobin as demonstrated by appropriate testing such as hemoglobin electrophoresis
* Receiving experimental therapy or investigational agents